A Question about Loudness of Sound....

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In summary: It seems to me that you are conflating two scenarios.If you are listening to a sound at a large distance from some small speakers, increasing the speaker area will increase the sound amplitude where you ear is located.If you are listening to a sound at a small distance from some large speakers, increasing the speaker area does little or nothing. The amplitude at your ears is equal to the amplitude at the source.
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Kaneki123
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OKay...Loudness of a sound is "the magnitude of sensation of human ear", or ''how much violently ear drum vibrates due to sound wave" (That is according to my understanding)...Now, increasing the area of vibrating body increases the loudness of sound...My question is that, if we increase area of vibrating body without changing its amplitude of vibration, then the energy per unit area will be the same, meaning the energy vibrating per unit of ear drum will be the same, meaning it will vibrate with same amplitude as before. So how can the loudness of such sound be increased?...Any help will be appreciated...
 
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Kaneki123 said:
My question is that, if we increase area of vibrating body without changing its amplitude of vibration, then the energy per unit area will be the same

True.

meaning the energy vibrating per unit of ear drum will be the same,

Why would you think that? Keep in mind that with a bigger source surface, there are many more paths from the source to a given spot on the eardrum. Those all add up.
 
  • #3
Kaneki123 said:
OKay...Loudness of a sound is "the magnitude of sensation of human ear", or ''how much violently ear drum vibrates due to sound wave" (That is according to my understanding)...Now, increasing the area of vibrating body increases the loudness of sound...My question is that, if we increase area of vibrating body without changing its amplitude of vibration, then the energy per unit area will be the same, meaning the energy vibrating per unit of ear drum will be the same, meaning it will vibrate with same amplitude as before. So how can the loudness of such sound be increased?...Any help will be appreciated...
It seems to me that you are conflating two scenarios.

If you are listening to a sound at a large distance from some small speakers, increasing the speaker area will increase the sound amplitude where you ear is located.

If you are listening to a sound at a small distance from some large speakers, increasing the speaker area does little or nothing. The amplitude at your ears is equal to the amplitude at the source.

If you want to increase the amplitude at your ear above that put out by the speakers, you could try a parabolic reflector.
 
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Kaneki123 said:
if we increase area of vibrating body without changing its amplitude of vibration, then the energy per unit area will be the same,
That's not true, actually because a small vibrating object just can't couple much energy into the air. A small loudspeaker cone will have to move much further than a large speaker cone, to set up the same Acoustic Power. This is why we use soundboards and other sorts of resonators if we want to make a musical instrument loud enough.
I may get complaints that that's too simple an argument but it is appropriate, I think, and covers most situations.
Launching and receiving sound waves is all about 'Matching Impedances' to maximise the transfer of energy at an interface. The well known Ossicles in the ear act as levers to match the impedance of air to the impedance of the fluid in the inner ear. (They do not 'amplify' the sound, as you will read in countless elementary articles about sounding hearing. Amplifiers need a power supply and the three bones have none.))
 
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Kaneki123 said:
OKay...Loudness of a sound is "the magnitude of sensation of human ear", or ''how much violently ear drum vibrates due to sound wave" (That is according to my understanding)...Now, increasing the area of vibrating body increases the loudness of sound...My question is that, if we increase area of vibrating body without changing its amplitude of vibration, then the energy per unit area will be the same, meaning the energy vibrating per unit of ear drum will be the same, meaning it will vibrate with same amplitude as before. So how can the loudness of such sound be increased?...Any help will be appreciated...
When we are close to a radiating aperture, which for the case of sound might be a vibrating diaphragm, we are in a Radiation Near Zone, also called the Fresnel Region. The shape of the radiated field is different to that at a large distance from the aperture, which is known as the Radiation Far Zone or Fraunhofer Region.
In the RFZ the diaphragm radiates a narrow beam with a number of weaker side lobes. In the RNZ it radiates essentially a parallel beam with blobs of energy dotted around. So a large diaphragm has increased directivity at great distances, increasing the received intensity, but reduces the intensity close up, because the energy is spread over a greater area.
In addition to this, if the dimensions of the diaphragm are smaller than about a wavelength, then, as mentioned by Sophie Centaur, the radiating efficiency is low. Sound waves from the front of the diaphragm are canceled by those from the back, and the diaphragm does not couple very well to the medium. This is because sound waves from the front of the diaphragm are canceled by those from the back. We say that the mechanical radiation resistance of the diaphragm has become small.
 

FAQ: A Question about Loudness of Sound....

1. What is the definition of loudness of sound?

The loudness of sound is a psychological sensation that corresponds to the physical attribute of sound intensity. It is measured in decibels (dB) and is perceived differently by individuals based on their auditory sensitivity.

2. How is the loudness of sound measured?

The loudness of sound is measured using a decibel meter, which calculates the sound pressure level (SPL) in decibels. SPL is determined by the intensity of the sound wave and the distance from the source of the sound.

3. What factors affect the loudness of sound?

The loudness of sound is affected by the intensity of the sound wave, the distance from the source of the sound, and the frequency of the sound. The sensitivity of an individual's auditory system also plays a role in perceiving loudness.

4. Can the loudness of sound be harmful?

Yes, exposure to loud sounds above 85 decibels for a prolonged period of time can cause damage to the auditory system, leading to hearing loss or other auditory disorders. It is important to protect your ears and limit exposure to loud sounds.

5. How can the loudness of sound be controlled?

The loudness of sound can be controlled by using earplugs or earmuffs in loud environments, avoiding prolonged exposure to loud sounds, and using soundproofing materials in buildings to reduce noise levels. Additionally, following workplace regulations and using properly maintained equipment can help control the loudness of sound in industrial settings.

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