Volume: Difference between revisions - Bose Portable PA Knowledge

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Here are some of the physiological reasons why this is the case:

1. The first one is the "equal loudness curve" (sometime also referred to as Fletcher-Munson curves) that Steve has already mentioned. The main effect is that you have to roll of the low end as level go up (or boost it as the level goes down). It basically compensates that the way humans turn sound pressure (physical property of sound) into loudness (a perception in our brain) is really not the same for all frequencies.

1. The first one is the "equal loudness curve" (sometime also referred to as Fletcher-Munson curves) that Steve has already mentioned (ed. see below). The main effect is that you have to roll of the low end as level go up (or boost it as the level goes down). It basically compensates that the way humans turn sound pressure (physical property of sound) into loudness (a perception in our brain) is really not the same for all frequencies.

2. The second is the “acoustic reflex” or “middle ear reflex”. It’s a ~~build~~-in protection in the middle ear that kicks in at sound levels above about 80 dB SPL. Normally sound is picked up by the ear-drum and then transferred through three tiny little bones in the middle ear to the inner ear. These bones that are basically a system of levers that transport vibration in a certain way. If it gets too loud a tiny muscles in the middle ear contracts and changes the coupling between the bones. It basically makes the levers less efficient and that protects the bones themselves and the inner ear from potentially harmful sound level. That fact also gives you some appreciation of what “evolution” regards as excessive sound levels and for what type of sound pressure levels the hearing system is basically designed for. So basically the acoustic reflex is a non-linear reduction in sound pressure level and its also frequency dependent

2. The second is the “acoustic reflex” or “middle ear reflex”. It’s a built-in protection in the middle ear that kicks in at sound levels above about 80 dB SPL. Normally sound is picked up by the ear-drum and then transferred through three tiny little bones in the middle ear to the inner ear. These bones that are basically a system of levers that transport vibration in a certain way. If it gets too loud a tiny muscles in the middle ear contracts and changes the coupling between the bones. It basically makes the levers less efficient and that protects the bones themselves and the inner ear from potentially harmful sound level. That fact also gives you some appreciation of what “evolution” regards as excessive sound levels and for what type of sound pressure levels the hearing system is basically designed for. So basically the acoustic reflex is a non-linear reduction in sound pressure level and its also frequency dependent

3. In the inner ear, vibrations are converted into never impulses by the so-called “hair cells”. These cells get wiggled by the incoming sound and as a result of that they send a nerve impulse. These impulses are all-or-nothing, i.e. they all have the same strength. More sound level leads to the hair cells firing more frequently, but not to any changes in pulse amplitude. Now the hair cells have a maximum firing rate, above which they just can’t react to more stimulus anymore. The only way to detect more sound pressure is to look at the behavior of a large group of cells which is much less exact as if every single cell would still be operating in its linear range.

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One other thing I'll throw at you for consideration, our ears have a different "eq curve" at different volumes ... yup, believe it or not, it may be that your ears are the "problem" here.

Check this ... go to Google and type in "Equal loudness curves" and you will get a bunch of hits that can explain it in many ways (even interactively). (edit: see [[Equal Loudness]]

Check this ... go to Google and type in "Equal loudness curves" and you will get a bunch of hits that can explain it in many ways (even interactively). (edit: see [[Equal Loudness]])

Here is an example from the studies, the threshold of hearing for a 1 KHz tone is about 3dB SPL. That is, for the average human ear, until you turn up your 1 KHz to 3dB SPL, it will not be loud enough.

@@ Line 8: / Line 8: @@
 Here are some of the physiological reasons why this is the case:
-.	The first one is the "equal loudness curve" (sometime also referred to as Fletcher-Munson curves) that Steve has already mentioned. The main effect is that you have to roll of the low end as level go up (or boost it as the level goes down). It basically compensates that the way humans turn sound pressure (physical property of sound) into loudness (a perception in our brain) is really not the same for all frequencies.
+.	The first one is the "equal loudness curve" (sometime also referred to as Fletcher-Munson curves) that Steve has already mentioned (ed. see below). The main effect is that you have to roll of the low end as level go up (or boost it as the level goes down). It basically compensates that the way humans turn sound pressure (physical property of sound) into loudness (a perception in our brain) is really not the same for all frequencies.
-.	The second is the “acoustic reflex” or “middle ear reflex”. It’s a build-in protection in the middle ear that kicks in at sound levels above about 80 dB SPL. Normally sound is picked up by the ear-drum and then transferred through three tiny little bones in the middle ear to the inner ear. These bones that are basically a system of levers that transport vibration in a certain way. If it gets too loud a tiny muscles in the middle ear contracts and changes the coupling between the bones. It basically makes the levers less efficient and that protects the bones themselves and the inner ear from potentially harmful sound level. That fact also gives you some appreciation of what “evolution” regards as excessive sound levels and for what type of sound pressure levels the hearing system is basically designed for. So basically the acoustic reflex is a non-linear reduction in sound pressure level and its also frequency dependent
+.	The second is the “acoustic reflex” or “middle ear reflex”. It’s a built-in protection in the middle ear that kicks in at sound levels above about 80 dB SPL. Normally sound is picked up by the ear-drum and then transferred through three tiny little bones in the middle ear to the inner ear. These bones that are basically a system of levers that transport vibration in a certain way. If it gets too loud a tiny muscles in the middle ear contracts and changes the coupling between the bones. It basically makes the levers less efficient and that protects the bones themselves and the inner ear from potentially harmful sound level. That fact also gives you some appreciation of what “evolution” regards as excessive sound levels and for what type of sound pressure levels the hearing system is basically designed for. So basically the acoustic reflex is a non-linear reduction in sound pressure level and its also frequency dependent
 .	In the inner ear, vibrations are converted into never impulses by the so-called “hair cells”. These cells get wiggled by the incoming sound and as a result of that they send a nerve impulse. These impulses are all-or-nothing, i.e. they all have the same strength. More sound level leads to the hair cells firing more frequently, but not to any changes in pulse amplitude. Now the hair cells have a maximum firing rate, above which they just can’t react to more stimulus anymore. The only way to detect more sound pressure is to look at the behavior of a large group of cells which is much less exact as if every single cell would still be operating in its linear range.
@@ Line 44: / Line 44: @@
 One other thing I'll throw at you for consideration, our ears have a different "eq curve" at different volumes ... yup, believe it or not, it may be that your ears are the "problem" here.
-Check this ... go to Google and type in "Equal loudness curves" and you will get a bunch of hits that can explain it in many ways (even interactively).  (edit: see [[Equal Loudness]]
+Check this ... go to Google and type in "Equal loudness curves" and you will get a bunch of hits that can explain it in many ways (even interactively).  (edit: see [[Equal Loudness]])
 Here is an example from the studies, the threshold of hearing for a 1 KHz tone is about 3dB SPL.  That is, for the average human ear, until you turn up your 1 KHz to 3dB SPL, it will not be loud enough.