Acoustic engineering, acoustic engineering and the concept of space as a support to optimize the acoustic engineering in electronics equipment acoustic instrument approach AMNIMARJESLOW AL DO FOUR DO AL ONE LJBUSAF thankyume

                                                          
                                                          

                                                                           X  .  I 
                                                              Acoustic  engineering

acoustic engineering

                                    

Acoustic engineering or acoustic engineering is the branch of engineering that is a practical application of the science of acoustics, including sound and vibration control, sound reproduction and broadcasting, as well as the use of sound instruments for measuring and checking or processing a variety of materials. Engineers in this field usually work through the design, analysis, and control sound.
One goal is the reduction of acoustical engineering unwanted noise, which can be called with a noise control. Unwanted noise could have implications for animal and human health to the hearing loss. Noise control principles are implemented into technology and design in many ways, including control by designing sound sources, designing the protective noise, sound-absorbing, damping, to use ear protectors.
However, acoustic engineering is not always about noise control, but also includes a positive thing as the use of ultrasound in medicine to programming digital sound through a synthesizer, designed the concert hall to improve the sound quality of the orchestra, to change the sound system in the train station so that the announcement comfortable to hear passengers , 


Based on the code of Physics and Astronomy Classification Scheme (PACS) used the Acoustical Society of America, sub disciplines of acoustic engineering is divided into:Aeroacoustic
Aeroacoustic learn how noise created from scaling the air through the turbulence and its movement through the air as a fluid. Aeroacoustic play an important role in understanding how noise created aircraft and wind turbines, as well as to explore the potential of musical instruments that are moved by wind.
Architectural acoustics

Architectural Acoustics (collectively, the acoustics of the building) is the application of engineering science in achieving good sound quality inside the building.
Underwater acoustics

Underwater acoustics is the scientific study of sound under water and dealing with the resulting sound natural and man-made, including how generated, movement, and perception of sound by animals. Applications include sonar to locate sunken objects, such as submarines, underwater communication by animals, sea water temperature observations for monitoring climate change, the search for a good fishing location by fishermen and marine biology.
acoustic musical
Acoustic musical examine and explain the physics of music and perception, how sound is used as the music. It includes the functionality and design of musical instruments including synthesizers; human voice (the physics and neurophysiological from singing); computer analysis of music and composition; the medical application of music therapy, and cognitive perception of music.
bio acoustics
Bio acoustics generally learn how sound is produced and heard in the animal world, including acoustic communication between animals and their relation to the behavior and evolution of animals; how sounds produced by animals; neuro physiological mechanisms of hearing and animals; the use of sound for monitoring animal populations, and human-generated sound effects to animals.
Electro acoustics
This acoustic engineering branch of science dealing with the design of the headphone, microphone, speakers, and so on. This branch of science is important due to the rapid increase of industrial electronic devices such as mobile phones, tablet computers, and so on.
Vibration and dynamics

Sub discipline studying the movement and interaction of the mechanical vibration system with its environment, including measurement, analysis, and control. This includes the vibration caused by the movement of trains and construction activity, vibration isolation to reduce noise, vibration control to protect bridges from earthquakes, to modeling the movement of vibration through the structure and buildings.

environmental noise
Studying environmental noise control noise and vibration caused by the traffic, aircraft, industrial equipment, recreational activities, etc., that could be regarded as disturbing noise. Acoustic engineers who study the acoustic environment face challenges in measuring and predicting noise levels, determine acceptable noise levels, and determine how noise can be controlled.

Voice signal processing

Voice signal processing is an electronic manipulation of the sound signal and a branch of digital signal processing. Voice signal processing is done by a variety of reasons, namely to improve the sound quality, eliminating unwanted noise, shrink the size of the sound signal so that the transmission is more efficient, and understand the contents of the voice signal.

controlling noise
Control of noise is a series of strategies to reduce noise pollution at the source, by blocking the movement of sound using the sound barrier, or by using ear protectors.

psycho acoustic
Psycho acoustic study the human response to what they hear, whether it's a noisy sound or music are beautiful. In various branches of acoustic engineering, human listener is the final destination answer whether a successful design.

ultrasonic
Associated with the ultrasonic sound waves in a solid medium, liquid, and gas at a frequency that is too high and can not be heard by humans. Its use includes ultrasonic underwater (sonar), nondestructive testing, sono chemical, material characterization, and medical ultrasound.  



                                                                      X  .  II  


                                                the effect of space in acoustic engineering  


Acoustic alone means the symptoms of sound changes due to the nature of reflective objects.
Room acoustics is very influential in the reproduction of sound, for example in the building meeting will greatly affect the clarity of speech . 


                                          

Acoustic space are linked to two things, namely:
point room acoustic system is way up a room so that the sound is not the noise disturbance in the rooms such as hall, stage, auditorium, or studio, it seems to me.
then there are several ways to design acoustic space that is the wall covering material, the shape of the wall, the arrangement of his own voice, the surface texture of the walls, and others.
to avoid the noise that could obscure the reflected sound direct sound absorbing material is needed to coat the walls, for example in the image below using layers of sound dampening: 


                                            

materials and material can vary are like gypsum, kalsi board, besides polyester material, texture can also be used to circumvent the reflection of sound, using a serrated textures can create a bias reflection sound to be broken and not audible to the ear.
  if you ever enter the room with the function of the theater, then you will not see the ceiling is flat, but with curves and sharp corners, this serves to reflect sound to a place far away from the theater audience. 


                                             

'' DEFINITION HOME THEATER ''
            Home theater is actually closer to home entertainment. a home theater system is actually a combination of the design of electronic components. There is a standard movie theater cinema has three speakers behind the screen, one on the left, middle and right side, and several other speakers who spread in space theater.
'' RECEIVER AUDIO / VIDEO ''
            Receiver audio / video and home theater amplifier in is actually a combination of different components. a home theater system can be built from separate components, examples of the components of the recipient:· For a video source can be either DVD.· Pre amplifier, and· Power amplifier for voice channels.

      Components such as DVD can be selected which components you want to fed to the unit output and pre amplifier.
'' SURROUND SOUND FORMAT ''
            There are two main sources of home theater surround sound formats, namely Dolby Laboratories and digital theater systems. Dolby Laboratories formats include various versions Dolby Digital and Dolby Pro Logic.

'' FOLLOWING HIM I WILL DISCUSS ON ACOUSTIC SPACES '''' SYSTEM ACOUSTIC SPACES ''

            Acoustics undefined space of forms and materials in a room that is associated with changes in sound or voice. acoustic space itself means the symptoms of voice change is bouncing objects or objects from nature. room acoustics is very influential in sound reproduction. lots of room acoustics linked by two things:
· Change the voice for reflection and· Disturbance sound.
'' Reflection, ABSORPTION, DIFFUSION ''

            Reflection of sound required for music and voice conversations, but too much loss in sound quality. reflection of sound is controlled by absorption or diffusion (diffused reflection). The following is the difference between reflection, absorption and diffusion:
· REFLECTION: There are several types of room reflections, all affect the sound system. hard surface reflection of near as hard as the original sound.
· ABSORPTION: how mostly to control unwanted reflections, through the use of absorbent foam or fiberglass.
· DIFFUSION: surface that is radiating, indirectly reflect or absorb sound, but spread out in different directions. Now designers emitting materials using irregular surfaces based on mathematical theory. 



                                                                     X  .  III  


                                      Characters Audio Signal In The Room (Room Acoustic)  


The purpose of using high quality loudspeaker and microphone with flat response characteristics, and equalization average sound system throughout a potential point of feedback, it is expected that the distribution includes a flat trajectory at audio frequencies that can be heard. Expected average output in this way, the level produced by the loudspeaker that reaches the microphone is never bigger than that produced a speaker without resulting in continuous oscillation. In other words, assume that the extra reinforcement provided by all the positive feedback spike issued balanced form of the losses were due to all the negative feedback.
Criteria Borner foundation for optimizing the geometry of the system is shown below, the microphone brought closer to the speaker so that many heard the microphone is the direct sound of the speaker. Loudspeakers far enough, be kind to reflection loudspeaker, so the direct sound from the loudspeaker not be a trigger factor of the feedback system. Assume that the listener is also in the field of reflective loudspeaker, it is possible that the sound level in the listening area with the settings on the system can not be greater than the speaker without help. In this case the position of the microphone with system setting off condition. By using the concept of delta system Borner, the situation on the maximum strengthening relations delta is one. (Delta is defined as the difference in decibels between the sound level at the microphone system when the system is off and the level of audience area while the system is on. 


                        

                                                             Picture Sound Room   


Although it has been described as a condition of maximum potential for strengthening the system, in practice the possibility delta can achieve greater than one. For example, if the microphone is used directly discriminate against the reflected field and the strengthening of other systems of 3 to 4 dB. Another possibility is to place the listener in the direct field of the loudspeaker, allowing the addition of strengthening the system. If the field is reflected in the level of the performance area is lower than in the listening area, generated additional system gain. This situation is described as a constant indoor Borner microphone in different areas of a seating area. Similar results may be notated in a room that has a floor area larger, relatively low ceilings and sound-absorbing substance. In such a room, the sound from the source point to the DC tends to decrease with a rate of 2 or 3 dB for every doubling of distance. Alternatively, increase the gain by pressing an electrically positive feedback on individual frequencies to filter very narrow band width.
If one channel can get all the energy frequencies negative feedback, strengthening potential system theoretically become infinite. Unfortunately, the acoustic feedback path is not stable enough to allow for this level of equalization narrow band. In other situations, the gain setting is achieved in the event of sustained oscillation. The system can not be operated satisfactorily at a point below the oscillation being incompatible comb filter response and the resulting ringing caused by positive feedback peaks. To return to the flat frequency response and a free ringing is heard, usually recommended system is matched appropriately, the system is operated under point 6 dB at maximum gain. Even in detail tuned system using a narrow band filter to operate on the strengthening of greater than 3 dB below sustained oscillation. 


                                                                     

                                                                      X  .  IIII  


                                                      propagation of sound waves  ( AUDIO ) 



Sound waves have a vibration that can propagate in the air, or water, or other material. The only place where the sound can not propagate is space vacuum. These sound waves have valleys and hills, valleys and hills of the fruit will result in one cycle or period. This cycle takes place repeatedly, thus forming the frequency of the sound waves.

Sound wave propagation is the process of sound propagation in wave propagation media (air, water, solids and other materials). Sound waves travel in the air around the differential approach 344 m / sec. This speed is relatively small depending on temperature and under normal room conditions can be ignored. The wavelength of sound is the distance between successive repetitions of the waveform as the sound travels through the air. Wavelength is expressed in the following equation:  


Wavelength = speed / frequency

lambda = speed / frequency

Where :

C = speed of sound wave propagation m / sec
f = frequency (Hertz)
λ = wavelength (m)

The period (T) is defined as the time required for one cycle of the waveform T = 1 / f. For f = 1kHz, then T = 1/1000 = 1 ms or 0,001 seconds, and λ = 344/1000 = 0.344 m.

The lowest sound that can be heard has a wavelength of 10 m and the highest having a wavelength as short as 20 nm. The scope is quite large and we will see this behavior stern voice. 


Basic aspects of Sine Waves 


 

Sine wave form is the basis for the formation of all the speech signal and music (sound waves). The image above shows the basic aspects of the sine wave. Waves can have the same frequency, amplitude and phase angle of the two can be different. The amplitude and phase angle relationship between the sine wave is determined how the combination of acoustic and electric. 



  

  

Study acoustics studies the production, transmission and sound effects. Acoustics engineering focuses on the design of sound systems and components such as microphone, headphone and speaker load. Musical acoustics concern on the development of musical instruments and a study of ultrasonic sound (sound frequency is too high for the human ear can hear)


Acoustics architecture studying the design of the rooms and buildings that have character optimal acoustics. It is very important for an auditorium, where all the audience should be able to hear the sound produced from a performance clearly and without echo. Architectural acoustics also must take into account the time the echo of a design space.  



                                                                    X  .  IIIII  

                                                                  acoustic space  


Acoustic space is defined as forms and materials in a room that is associated with changes in sound or sounds that occur.
Acoustic alone means the symptoms of sound changes due to the nature of reflective objects or passive objects of the universe.
Room acoustics is very influential in the reproduction of sound, for example in the building meeting will greatly affect articulation and clarity of the speaker.
Acoustic space are linked to two fundamental things, namely:

    Voice change due to reflection and
    Voice disorders due to the strength of penetrating sound from the other room.
It takes an expert calculations based on theory and field experience to create an ideal space, such as home theater, karaoke room, record room, meeting rooms and the like, including places of worship space.
Measurement ranges in frequency and magnitude, can be done with the help of an R T A (Real Time Analyzer) to assess and determine the frequency of the reflected or force a break, so it can be determined the type of sound-absorbing material used.
acoustic space
Many highly effective absorbent material to be used, for example Tra Flex. Have many variants product that allows to create optimal results. Tra Type Flex 10:15, with specification of alpha = 0.7 at 300Hz-16KHz, highly effective if used to clarify the voice.  


       acoustic space at the theater   




      acoustic space   



                                                                 X  .  IIIIII  

                                                       characteristics of hearing  


If sound can be heard, the amplitude of the sound is said to be above the threshold, and if the sound is inaudible, the amplitude is considered to be below the threshold. amplitude noise at the transition point between the ability to hear and inaudible is defined as the hearing threshold. When the amplitude of the noise exceeds the threshold, the sound is processed and considered to have certain qualities include loudness, pitch, and a variety of other perceptive nature of such information. The study of auditory perception in relation to the physical characteristics of the sounds included in the field of psycho acoustics.
Sensitivity (sensitivity)
The ears are not always sensitive to all frequencies. Absolute sensitivity of the ear, is defined by a threshold, depending on various factors, the most important is the sound pressure level and frequency of sound. the resonance of the ear canal, the effect of the level of ossicles , and the difference between the surface area of ​​the eardrum and footplate all affect the intensity of the sound that penetrates the cochlea.
Audiometer that generate signals with variable frequency and intensity used to measure a person's hearing sensitivity. The signals generated by the audiometer can be directed either to earphones or speakers in the anechoic chamber. Because it is much more difficult to ensure the sound intensity at the level of the cochlea, and such determination will not accurately represent how well a person hears under normal circumstances, we usually determine hearing sensitivity in terms of the threshold for the sound of various frequency sound pressure levels specified in the field of sound without their listeners  


most work in clinical audiology requires measurement that refers to a single ear rather than the ears. This is usually done by directing a test signal to the right earphone headset rather than the loudspeaker. Used headset as opposed to exposure to a loudspeaker. For example, the resonance frequency of the ear canal is shifted due to the second end of the canal is sealed in contrast to the situation when the canal is open to the sound field. In addition, the placement of the earphones can cause unwanted physiological noise that can interfere with the detection of low-frequency sound. Also, methods of calibration sound of loudspeakers is different from that for calibration of sound from earphones . 


loudness
loudness related to the amplitude of the sound above the threshold, loudness is not perceived by the human ear in the same size as the amplitude increases during different frequencies above the threshold.
tone
The tone was clearly related to the frequency. the actual pitch of the sound is influenced by other factors, including the level of sound pressure and frequency components. The average adult male voice between 120 and 150 Hz and for women lies between 210 and 240 Hz. But we generally find it easy to distinguish between the voices of men and women though. The spectrum of the sound produces the sensation of psychological quality. This allows us to distinguish the difference, for example, between a trumpet and other music instrument. This is due to differences in each - each sound spectrum (ie, the contents of their frequency or tone), which in turn, is a function of complex vibrations and resonance modes inherent in each structure. We also able to distinguish speech sounds different because of the difference in the sound spectrum. Even over the phone, the voice of individuals recognized for their sound spectrum differences.
masking
Masking occurs when the ability to hear sounds connected with the absence of noise or other background noise. The effect of "Cocktail party", which makes it difficult to have a private conversation with the background chatter of others, is an example of masking. most of the intelligence in the speech generally in the frequency range between 200 Hz and 6 kHz. But too loud noise each frequency band can affect speech intelligibility as the excess of the auditory system that a person can not effectively distinguish speech from the total signal is valid.
Someone speak normally produce a sound level of 55-70 dB at 1 m. It is harder for people to speak louder for a sustained period. A maximum effort distinctive voice, in the form of screams, produces around 90 dB at 1 m. Speech clarity generally increases when the speaker and the listener are close to each other and if the speaker improves the signal-to-noise (S / N) ratio by talking loudly. Maximum clarity can usually be obtained if the level of speeches between 50 and 75 dB at 1m from the speaker. speak louder does not always guarantee greater clarity, although the S / N ratio (defined as the intensity of the signal divided by the intensity of the noise) can be improved. If the listener is familiar with the words and dialects used, will be greater clarity. It is for that reason that communication is important, especially air controllers, is based on a limited vocabulary .In regular face to face conversation, the listener has the additional advantage related to the context of the words by observing facial expressions and gestures of the speaker.  



                                                             X  .  IIIIIII  

                                PHENOMENON OF ACOUSTIC ROOM CLOSED  



In an enclosed space, acoustic energy propagation path is the room itself. Therefore, knowledge about the phenomenon of sound that occurs in the room will be very decisive when necessary controls in the room heard the conditions according to function. The phenomenon of sound in the room can be depicted in the sketch below:  


                             


Bayangan sumber  = shadow sources 
Dinding ruangan memantulkan suara  =  The room walls reflect sound  
komponen suara pantul  =  reflective sound components 
p titik pengamatan  = p observation point 
Komponen suara langsung  =  Direct sound components 


From these sketches, it can be seen that at any observation point or points where people who enjoy the sound (the audience) will be influenced by the sound of two components, namely component of direct sound and reflective sound components. Direct sound component is a component sound reached the ears of the listener directly from the source. The amount of sound energy that reached the ears of the noise component is influenced by the listener distance to the sound source and the effect of energy absorption by air. Reflective sound components are components of sound to the listener's ears as the sound interacts with listeners around the room surfaces (walls, floors and ceilings). Total energy sound to the listener's ears and the audience's perception of the sound heard will of course be influenced by both of these components. That's why the reflected sound components will be very instrumental in shaping perceptions of hearing or bias also mentioned surface acoustic characteristics in the room will greatly affect the condition and perception of hearing experienced by the listener.
There are two extremes related to the characteristics of indoor surfaces, ie when all indoor surfaces are highly absorbent and all indoor surfaces are highly reflective sound energy to him. When the surface is very absorbing in the whole space, then the component sounds to the listener only direct component only and the rooms were like this is called an anechoic chamber (anechoic chamber). While in space that the entire surface is highly reflective of energy, then the reflected sound components will be far more dominant than its direct component, and commonly referred to as room reverberation (reverberation chamber). The room that we use is generally located between two extremes, according to function. Recording studio space for example closer anechoic chamber, while the hard-walled room that is headed to the room reverberation.
Acoustic design of indoor spaces are essentially controlling the direct and reflected sound component of this, by determining the acoustic characteristics of indoor surfaces (floors, walls and ceilings) in accordance with the functions of his office. There is room for functions require more absorptive characteristics (studio, Home Theater, etc.) and there that require a combination of absorptive and reflective impartial (auditorium, classrooms, etc.). By combining several surface character of the room, a designer can create a wide variety of acoustic conditions hearing in accordance with the function of his office, which is manifested in the form of acoustic parameters of the room.  


Acoustic characteristics of the room surfaces are generally divided into:

    Sound Absorbing Materials (Absorber) ie surface made of a material that absorbs some or most of the sound energy that came to him. For example glasswool, mineral wool, foam. Material may manifest as a stand-alone or incorporated into the absorber system (fabric covered absorber, the absorber panel, grid absorber, the absorber resonator, perforated panel absorber, acoustic tiles, etc.).
    Materials Sound reflectors (reflectors) that the surface is made of material that is reflecting most of the sound energy that is coming to him. The resulting reflection is specular (following the rules Snelius: angle of incidence = angle of reflection). Examples of these materials, for example ceramics, marble, metal, aluminum, gypsum board, concrete, etc.
    Materials pendifuse / spreader sound (diffusor) which made the surface uneven spreading acoustically sound energy that comes to him. For example QRD diffuser, BAD panel, etc. diffsorber.
By using a combination of three types of materials that can diwujdukan hear the desired conditions according to function.
Acoustic parameters are typically used in confined spaces can be broadly divided into two, namely the parameters of temporal monoaural that can be felt by using one ear only (or measured using a single microphone) and the parameters that are spatial binaural that can only be detected by 2 ear simultaneously (or measured using two microphones simultaneously).
Which is included in the temporal - monoaural type parameters are:

    Reverberation time (T or RT), ie the time required for a sound energy decays (by 60 dB) from the source of the sound is turned off. This parameter is the acoustic parameters used earliest and still the most popular parameter in the design of indoor spaces. Reverberation time used in the design example RT60, T20, T30 (subscript indicates decay range used to estimate the decay of energy) and EDT (based on a 10 dB decay at the beginning). The last parameter is more often used because it contains significant information from the observed sound field. The price of these parameters will be influenced by the function of the room, the volume and surface area of ​​the room, and is different for each position of the listener. Suppose for a studio room needs to be <0.3 s, 0.7 s classrooms, concert hall 1.6 - 2.2 s, the mosque 0.7 - 1.1 s, 2 s cathedral etc.
    Clarity, the logarithmic ratio of sound energy in the early 50 or 80 ms to the sound energy afterwards. Embodied within the parameters of C80 to C50 for music and speech. This parameter associated with signal fidelity sound perceived by the listener in the room. (Standard costs about -2 to 8 dB)
    Intelligibility, ie comparison of the initial energy of the total energy of 50 ms. Usually expressed as D50 and more are used to express the clarity of sound pronunciation (speech). The suggested price is> 55%. (Related parameter is STI or Rasti or% Alcons).
    Intimacy, as indicated by the difference between the sound coming directly to the initial reflection at each point the listener. Stated in the Initial Time Delay Gap (ITDG). The suggested price generally is <35 ms (most preferably 15-20 ms). This value is still influenced also by how quickly (rhythm) sound source .. 

Which is included in the parameter-type spatial binaural is LEF and IACC. LEF is obtained by measuring slammed Impulse Response indoor use 2 microphones placed close together, a single microphone with omnidirectional and the other patern patterned Figure of Eigth. While IACC obtained by the impulse response measurement using two microphones embedded in the two human ears (or both ears clone a human head, dummy head). From these two parameters can be derived parameters and wide envelopment staging / source (apparent source width).

The above concept more usually applied in a large room. For smaller rooms such as studio, a parameter again to note that the distribution of modes (resonant frequency) space, especially at low frequencies.  

                                                               X  .  IIIIIIII 

 

  
                                                               bio acoustics   

Discuss bio-acoustic means trying to unravel the relationship between sound - sound waves, vibrations and the sound source with health. What does it mean that wave? and what to do with your ears? Are there any benefits of a sound wave in health?It's essentially the first ....
Wave
    
  

 Wave propagation is a phenomenon of interference, namely energy propagation. This propagation direction can propagate in one dimension (eg rope deviation waves), two-dimensional (eg water surface waves), and three-dimensional (eg, the sound waves in the air).
Based on the direction of propagation, the wave can be divided into:• Longitudinal Waves ie the direction of wave propagation is parallel to the direction of motion of the particles of the medium.• Transverse wave is wave propagation direction perpendicular to the direction of motion of the particles of the medium.
Based on the mechanism, the waves are distinguished:• A wave of rapid mechanical waves may depend on the extent its resonance vibrations mechanics.• elastic wave is a wave that quickly its resonance vibrations depending on magnitudes of elasticity.• Surface waves in a substance cait waves may quickly its resonance vibrations depending on the amount of the liquid surface.• Electromagnetic waves are waves that quicklyits resonance vibrations  depending on the amount of electrical and magnetic.Medium in the process of propagation does not always come on the move along with the wave propagation. For example, sound propagates through the air medium will make the air particles moving oscillations (local) only.
Beep Beep & WavesThe concept of sound in everyday life associated with the sense of hearing (ears). Human audible frequency is f = 20 _ 20000 Hz (audible frequency). Another type of sound wave is f Ultrasonic> 20000 Hz and infrasonic f <20 Hz.Sound waves are longitudinal mechanical waves that are in the area we are hearing is 20 Hz to 20,000 Hz and the propagation requires a medium, the medium can be either solid, liquid and gas.Fast sound waves in the air at a temperature of 0 ° C or 273K is approximately 331.3 m / s.
In addition to frequency, another factor that affects the sound that can be heard is good enough sound energy. Energy sound waves is determined the frequency and amplitude of the wave and intermediate object E = ½ m ω ^ 2A = 2 (rho) (Phi) f ^ 2AE = the power density wave (J)rho = density of the medium (kg / m3)ω = angular frequencyf = frequencyA = amplitude
The intensity of the wave (sound)Sound intensity is the amount of sound energy (sound power) per second per unit area in the perpendicular direction.I = P / AI = intensity of sound (W / m2)P = sound power (watts)A = area (m2)The smallest sound intensity is still heard by humans is called the threshold pemndegaran:Io = 10 ^ -12 watts / m2 at a frequency of 1,000 HzThe intensity is still heard by humans without a pain-called "threshold of hearing".Is = 10 ^ o = 1 watt / m2The sound intensity is inversely proportional to the square of the distance the listener to the source.I1: I2 = (1 / R1 ^ 2): (1 / R2 ^ 2)
The sound intensity levelSound intensity level sound intensity ratio is the logarithm of the intensity threshold of hearing.TI = 10 log units deci Bell (dB)
This matter will be discussed in the ear as the organ of hearing, the ultrasonic waves and benefits as well as the noise ... in the next article include hearing loss (deafness), hearing test and supplementary material
 Ear as a hearing instrumentear is the organ of hearing and balance, consists of the outer ear, the middle ear and the inner ear.outer ear picks up sound waves are converted into mechanical energy by the middle ear. middle ear transform the mechanical energy into nerve impulses, which are then delivered to the brain. the inner ear also helps to maintain balance.anatomy of the ear-150x150outer earouter ear consists of the ear (pinna or auricle) and the ear canal (external auditory meatus). the outer ear is cartilage (cartilage) that is covered by skin, earlobe rigid but also flexible. sound captured by the ear flow through the ear canal to the eardrum. eardrum is a thin membrane that is covered by skin, which separates the middle ear outer ear.middle earmiddle ear consists of the eardrum (tympanic membrane) and a small space filled with air that has three small bones that connect the eardrum to the inner ear. The third bone is:• malleus (shaped like a hammer, is attached to the eardrum)• incus ( malleus and stapes)• stapes (pda attached to the oval window at the entrance to the inner ear).the vibrations of the eardrum are mechanically reinforced by bones and delivered to the oval window. middle ear also has two small muscles:tensor tympani muscle (attached to the malleus and keep the eardrum remain attached) stapedius muscle  

                                        

the vibrations of the eardrum are mechanically reinforced by bones and delivered to the oval window. middle ear also has two small muscles:tensor tympani muscle (attached to the malleus and keep the eardrum remain attached) stapedius muscle (attached to the stirrup and stabilize the relationship between stapedius oval window.if the ear receives sound harsh, then the stapedius muscle will contract so that a series of increasingly stiff bones and little sound is delivered.This response is called the acoustic reflex, helps protect the delicate inner ear from sound damage.The eustachian tube is a small tube that connects the middle ear to the back of the nose, allowing the entry of outside air into the middle ear.The eustachian tube opens when we swallow, thus helping to maintain the same air pressure on both sides of the eardrum, which is important for normal hearing function and comfort.
ear inthe inner ear (labyrinth) is a complex structure, which terjdiri of two main parts:• cochlear (auditory organ)• semicircular canal (organ of balance).cochlea is a hollow channel which is shaped like a snail's shell, consisting of viscous liquids and corti organ, which contains thousands of tiny cells (hair cells) that have hair that leads into the fluid. vibration sound is delivered from the bones of the middle ear to the oval window in the inner ear causes bergetarnya fluid and hair cells. Different hair cells respond to different sound frequencies and convert it into nerve impulses.These nerve impulses and then walk along the auditory nerve fibers that will take him to the brain. although there is no protection from the acoustic reflex, but the sound of rumbling could cause damage to the hair cells. if the hair cell is destroyed, it will not grow back. if the ears constantly receiving loud noise may occur progressive hair cell damage and hearing loss. semicircular canal is a 3 channel filled with fluid, which helps maintain balance. every movement of the head causes aquatic inside the channel moves. fluid movement in one channel can be larger than the movement of fluid in the other channel; it depends on the direction of movement of the head. This channel also contains hair cells that respond to fluid motion. The hair cells initiate nerve impulses that tell the brain which way the head is moving, so that a balance can be maintained.if there is an infection in the semicircular canal, (as occurs in middle ear infections or flu), they can arise vertigo (spinning feeling).  

ULTRASONIC

To learn ultrasonic, we must remember first about the classification of sound frequencies. Ultrasound is sound waves with a frequency of 20,000 Hz.
Ultrasonic devices can be produced with an electric magnet and a piezoelectric crystal with a frequency above 20,000 Hz.
magnet electricity
If the ferromagnetic rods placed on an electric magnetic field will arise ultrasonic waves in the ferromagnetic rod tip. Similarly, if the ferromagnetic rods circled wire, then electrified. 

   

Ultrasound diagnostic tool using ultrasonic waves having a frequency of 1-10 MHz. The speed of sound waves in a medium will be different than any other medium. Acoustic properties of the medium determine this difference. The frequency and ultrasonic power used in medicine adapted to the needs. For diagnostic use frequency 1-5 MHz with a power of 0.01 W / cm2. for therapy improved power to 1 W / cm2, even to destroy cancer necessary power of 103 W / cm2.Reduction in the intensity of the attenuation, which can be caused by a mechanism, reflection, refraction, absorption and scattening.Effect of ultrasound attenuation in:1. Attenuation will limit the ability of ultrasound to examine body tissue structures are at only up to certain limits to the innards.2. The existence of different attenuation in body tissue will provide an overview of ultrasound different.3. Ultrasound tool difficult to use to examine the structure of the bone tissue of organs that contain gas.Basic use of ultrasonic Doppler effect, namely a change in frequency due to movement and vibration listener or otherwise sent to the object to be reflected by the object itself.
Ultrasonic Wave EffectUltrasonic waves can provide good effects of mechanical, thermal, chemical and biological. Or changes - cyclic changes that occur in the propagation of ultrasonic gel: particle vibrations, pressure changes, delta density, and temperature changes.All the above changes are temporary and effect very small, the amount of heat that arises in the tissues of the body is determined by: the intensity, duration of exposure, and the absorption coefficient network. The use of ultrasonic gel and high intensity can cause cavitation phenomenon in which a liquid medium. Factor that increases the security of the use of ultrasound is widely used today has the intensity of <10 MW / Cm2.mechanicsForming emulsion smoke / clouds and disintegration of some solid object. It can be used to detect the location of gallstonesHotMost ultrasonic experiencing reflection at the point in question, and partly on the point of changing the heat. On the network cavity formation can occur with high intensity.ChemistryUltrasonic waves cause oxidation and hydrolysis of polyester tiesBiologicalThis effect is actually a combination of the above effects, such as heat cause dilation of blood vessels. Ultrasound also increases the permeability of cell membranes and capillaries and stimulate cell activity. Muscle paralysis and destroyed cells, bacteria and viruses can also be destroyed. Fatigue will occur if the ultrasonic frequency increased.  

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                                                              Acoustic Wave nature  

                                                                    

Wave propagation is a symptom of a disturbance through a medium in which after the disorder through the state of the medium will be back to normal. Medium is a collection of objects that interact where fault propagates. Based on the propagation medium, the waves are divided into two types:1. Wave Mechanics, waves may occur due to mechanical forces that propagate in the medium. Examples: sound waves, acoustic waves2. Electromagnetic Waves, waves may not require the propagation medium because it can propagate in a vacuum and resulting change is not a change in mechanics. Example: Radio Waves
Under the direction of propagation, the wave is divided into two, namely:1. Transverse wave, the wave propagation direction perpendicular to the direction of vibration medium2. Longitudinal Wave, wave propagation direction parallel to the direction of vibration medium.When a wave propagates from one medium to another it will experience two conditions that the wave will be reflected in the direction of propagation satisfies the principle foundations of thought and reflection second wave conditions will be forwarded through the next medium.
            Based on the wave frequency is divided into three parts:1. infrasonic waves with a frequency lower than 20 Hz,2. The wave had audiosonic with a frequency of 20 Hz to 20 KHz,3. The ultrasonic waves with frequencies greater than 20 KHz.
Wavelength used in the echo sounder which ultrasonic waves. A propagating wave vibration, the vibration is a movement back and forth repeatedly through the point of imbalance. Vibration on a simple swing is done by tying a light load on a rope, has a style that is proportional to the deviation. The direction is always toward a balanced position. . The frequency of the wave is the number of waves that occur in one unit of time. Frequency is denoted by the letter "f" and with Hertz or commonly abbreviated Hz.f = 1 / T
The period is the interval of time required to take one wave. Period denoted by the letter "T" and the unit is second. What is called the perfect wave on a transverse wave is the wave motion of a balanced position to crest and then back to a balanced position and then into the trough to return to a balanced position. Waves that propagate straight from one point to another takes time, in other words, the wave has the speed to propagate. So the wave propagation speed is the distance traveled by a wave in unit time. Fast wave propagation is given the symbol "V" with units of m / sec.
V = λ. f = λ / T
Sound consists of regular movements of molecules of an object that is elastic. Because of the elastic nature of the movement of particles in a material, such as the movement caused by the sound source, be forwarded to the nearest particles. Therefore the sound waves that propagate from a source has the same speed as the speed of sound. In the fluid particle motion is forward and backward parallel to the direction propagation. Because the fluid is compressible, this movement resulted in a change in pressure can be detected by a pressure-sensitive hydrophones.
1. Acoustic ImpedanceIn the ultrasonic waves are acoustic impedance that affects the reflection of the wave. The acoustic impedance can be used to determine the type or characteristics of the medium through which the wave. Additionally impedance acoustic waves also determine the events that occur when a wave of waves passing through the boundary between two different mediums. Acoustic impedance (Z) is defined as the product of density (ρ) of the medium is perpendicular waves of sound and sound propagation velocity (c) in the medium. The units of the acoustic impedance is kg / (m2sec) and is often expressed in rayl, where 1rayl = 1 kg / (m2sec).Z = ρca. Information:b. = ρ is the density in kg / m3c. c = speed of sound in m / sThe difference in acoustic impedance of the boundary is large, such as water and rock, sound energy comes almost entirely reflected, but if the difference is less like water and mud, the reflected only a fraction of the energy of noise coming and then the rest of the energy is continued to another part. Impedance acoustic have a role:a. Determination of transmission and reflection wave of the boundary between the two materials have different acoustic impedanceb. designing transducerc. Estimating the absorption of sound waves in a medium

2. Reflection (Reflection)When a sound wave through the boundary between two media with different materials, each of which has a different sound propagation speed, then some energy sound waves it