So called "Music and Audio Production"

[fishmonkey]

yep, what he said.

you are thinking about a sound wave as a static/standing wave, when it is actually flowing back and forth, past and through you.

of course, in a room you are hearing a bunch of reflections and interactions of the waves too, so that can mess things up really badly. however, in most cases (and especially with bass, since a lot passes through the walls) the reflections are weaker than the original signal, and don't completely cancel it out.

if your logic was true, headphones wouldn't work either, since most sound waves don't "fit" inside headphones in the way you describe...

Loving it so far. The headphone argument is a good one. So it makes me think that there are two ways (and maybe more) in which we experience frequencies.
1. Their Intensity &
2. The wave itself
Also the reflections.
That may be why we appreciate music better in room that can accommodate all of these characteristics.
Otherwise, we are really listening to compressed versions of the sound. Kind of like mp3 compression.

the main issue with sound in rooms is that the reflections and admixes of sound waves can significantly distort the original sound. at the same time, we live in a fundamentally reflective world, and in everyday life reflections contain important additional information, including information about the structure and texture of the space around us, and the location of sound sources. being in an anechoic chamber is a very odd experience—since there are no reflections, it sounds and feels very "dead".

if you want to learn more, this is one of the best texts:

https://www.amazon.com/Introduction-Psy ... 9004252428

[Nokatus]

Loving it so far. The headphone argument is a good one. So it makes me think that there are two ways (and maybe more) in which we experience frequencies.
1. Their Intensity &
2. The wave itself

It seems to me you are just somewhat misunderstanding the "wave" bit in how we hear sound, guessing from you separating the intensity and "the wave itself" in this manner. Talking about hearing sound through the air, the intensity has got all to do with how great the pressure changes are, nothing more. You can't hear that separately from "the wave itself", as it's a property of the sound event you are sensing. You hear changes in pressure, full stop. The way those changes in pressure propagate through the air is described as longitudinal waves. However, when you are hearing "oh cool, the air pressure in my ear canal fluctuates 60 times a second", that's all you are hearing (a 60 Hz tone), periodic fluctuations in the pressure.

[evon]

Your point is taken Nokatus. I was wrongly theorizing that the intensity of the displacement of the air particles that are propagating the wave would give our ears the same experience of the frequency even before the wave has been completed.

However, I am still not seeing any explanation as to how one is able to hear a 60Hz sine wave in a room with no dimension bigger than say 16ft. Based on the theory I have learned, we should only be hearing the higher octaves and/or the other partials that make up the tone if it is not a pure wave.

And with the headphones, are we really hearing the frequencies or is our brain filling in the dots?

[Nokatus]

However, I am still not seeing any explanation as to how one is able to hear a 60Hz sine wave in a room with no dimension bigger than say 16ft. Based on the theory I have learned, we should only be hearing the higher octaves and/or the other partials that make up the tone if it is not a pure wave.

And with the headphones, are we really hearing the frequencies or is our brain filling in the dots?

If you have to ask this, you didn't really get what I was saying

The wave "fitting inside the room" (also when thinking of headphones) is irrelevant from the point of view of actually being able to hear a particular frequency. As a thought experiment, think of it this way: if you had a device that could simply alter the air pressure in your ear canal, and nothing more, and then you made it alter the pressure so that high and low pressure points happened at certain frequencies and intensities, that's all it would take for your ear drum to move accordingly (push inward when in high pressure, outward when in low pressure), consequently making you hear the sound in question. Incidentally, there's a catch in this example, as this is actually quite an accurate description of a perfectly sealing in-ear monitor. Separating the very small airspace between your eardrum and the front element of the in-ear plug, they have an acoustic element that vibrates (i.e. pushes towards your ear, causing the air pressure to rise in the airspace, and conversely also retracts towards the plug itself, causing the air pressure in the airspace to lower). Your eardrum moves, you hear sound. The wave "fitting inside the room" (in this case, the tiny space between your eardrum and the moving element on the in-ear tip of the earplug) doesn't quite factor into that, in the way you believe.

[Da hand]

However, I am still not seeing any explanation as to how one is able to hear a 60Hz sine wave in a room with no dimension bigger than say 16ft.

Please read my earlier post again. I gave an explanation on exactly that

Take a look at my scanner analogy again in my post and in the second scanner image think of the paper as being the sound wave. See how the paper is much longer than the scanner and it still all gets scanned perfectly? The same thing happens with our ears. The sound wave can be much longer than our ears, but gets scanned by our ears as the wave is passing us.

All this happens before the sound hits any walls in the room - because the direct distance between the sound source and our ears is the closest - and therefore, before any chance of the room influencing at all the sound in our ears.



What the room influences are the reflections of the initial sound from the walls, ceiling, floor. The sound emanating from the sound source travels in all directions at the same time. As the sound hits our ears, at the same time it also rebounds off walls, ceiling, floor, etc. However, the sound that has been reflected has traveled a longer distance to reach our ears and, therefore, arrives later at our ears.

These reflections will combine to create the "reverb" you get in the room and also any standing waves occurring at very specific frequencies. These can influence, to a degree, any new sound being played after the initial sound (if the reflections of the initial sound arrive at our ears at the same time as the new direct sound), but they don't limit what direct sound frequencies we can experience because of the room size.

If you made all the surfaces of the room fully absorbent, you would still hear all the frequencies of the direct sound the speakers are capable of reproducing, independent of the room size.

Based on the theory I have learned, we should only be hearing the higher octaves and/or the other partials that make up the tone if it is not a pure wave.

What theory is that exactly? Which part of what you learned leads you to think that the room dimension plays a role in what direct frequencies (not reflected frequencies) you can hear?

And with the headphones, are we really hearing the frequencies or is our brain filling in the dots?

Again, yes we are hearing all the frequencies. Take a look at my scanner analogy again

Also, think how close the headphone drivers are to our ears - at most a couple of centimeters. And earbuds are even closer! Let's take a conservative measure of about 5cm from headphone driver to eardrum (ear drum distance from the Pinna to Ear Drum is about 2.5cm). A 5cm sound wavelength gives us approximately a 7khz (that is 7000 hz) frequency. So in your thought process above, all the sound below 7khz would not exist in the headphone space and our brains would have to fill in everything occurring below 7khz - that would be impossible!

[fishmonkey]

However, I am still not seeing any explanation as to how one is able to hear a 60Hz sine wave in a room with no dimension bigger than say 16ft. Based on the theory I have learned, we should only be hearing the higher octaves and/or the other partials that make up the tone if it is not a pure wave.

i think maybe you are still assuming that the air in the room is vibrating like a guitar string. as mentioned by a few people earlier, it is not. a guitar string creates sound by vibrating in a transverse standing wave. that means that the frequency of the vibration is limited by the length and stiffness of the string.

the sound that your ears pick up is in the form of longitudinal pressure waves travelling past you through the air. the whole wave does not need to exist in the room in one static wave for you to hear it. you are not hearing the whole sound wave in one single snapshot.

http://www.physicsclassroom.com/mmedia/waves/gsl.cfm

imagine two extreme cases:

1. you are in a "free field" listening environment, e.g. in the middle of a vast desert with no walls anywhere near you. if a sound wave leaves a speaker in front of you, once it passes you it continues on until the energy eventually dissipates into the air.

2. you are in an anechoic chamber, where the walls absorb all sound waves that reach them. if a sound wave leaves a speaker in front of you, once it passes you it is fully absorbed by the walls.

in both cases you will hear the same sound.

if the walls are reflective, then the part of the wave that is located where your ears are can be affected by reflections of itself. that is a more complicated case, but the same fundamental principles apply.

[Da hand]

^ as well as what fishmonkey wrote. Took me a while to edit my post

[evon]

Yes, discussions like these are very helpful. Da Hand and fishmonkey somehow was able to give me a good picture. Although all the others tried.

The key word for me was that the wave is not "static". and that the room itself is not vibrating.

Nokatus tried, but his analogy of the scanner was only good for trying to explain how the wave "passes through" our ears, but seemed to strengthen my skewed argument. Because that was how I was seeing it. Like feeding a foolscap paper through a scanner, but having only letter size paper for it to be printed on. The letter size paper would be my 16 ft room, and the 60Hz wave would be the information I wanted to print.

However, it is much clearer now and I can see (hear) why we don't need a certain dimension to hear those frequencies. Also why the headphones are able to facilitate these bass frequencies.

Also, thanks to Tarekith who left the explanation to you guys.

Just an aside though: I wonder how many of us visualize these characteristics while working in sound? When Eqing, compressing etc. I have never done this, but gives me the idea to do some experiments.

This may very well by my new topic in the "Music and Audio Production" subforum.

[Nokatus]

Nokatus tried, but his analogy of the scanner was only good for trying to explain how the wave "passes through" our ears, but seemed to strengthen my skewed argument. Because that was how I was seeing it. Like feeding a foolscap paper through a scanner, but having only letter size paper for it to be printed on. The letter size paper would be my 16 ft room, and the 60Hz wave would be the information I wanted to print.

It wasn't me who used a scanner analogy. Imo it is a flawed way to present this in a simplified context, exactly because it tries very nicely to capture the idea but can cause (perhaps slightly different) misconceptions on the topic instead.

[evon]

Nokatus tried, but his analogy of the scanner was only good for trying to explain how the wave "passes through" our ears, but seemed to strengthen my skewed argument. Because that was how I was seeing it. Like feeding a foolscap paper through a scanner, but having only letter size paper for it to be printed on. The letter size paper would be my 16 ft room, and the 60Hz wave would be the information I wanted to print.

It wasn't me who used a scanner analogy. Imo it is a flawed way to present this in a simplified context, exactly because it tries very nicely to capture the idea but can cause (perhaps slightly different) misconceptions on the topic instead.

My humble apologies, Sir.

[Nokatus]

no worries