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Why is sound quality subjective? - Page 2

post #16 of 38
Thread Starter 
Quote:
Originally Posted by Keithpgdrb View Post
I forgot which company right now, but they developed a mic that reproduced the voice exactly, with no coloration at all, and people hated it, it was a flop. thats why some old vintage microphones are sought after. they color just right. so even from the dawn, we have been focused on making good sounding recordings, not necessarily "accurate" recordings.

as they say, "its all in the mix"
That's interesting. It would be cool to see some research as to why it flopped. Were the performers just not as "good" as people thought they were with the distorted recordings, or was it just that people prefer to hear an altered version?
post #17 of 38
Well measuring sound accuracy (or more generically, signal accuracy) is very common and done all of the time. It doesn't seem to be common in the hobbyist audio world though. Unless you need equipment specifically to reproduce the source as accurate as possible (Studio Monitors for Professional Audio Engineers for example), you probably want some coloration in your music reproduction.
post #18 of 38
Quote:
Originally Posted by jvgig View Post
That's interesting. It would be cool to see some research as to why it flopped. Were the performers just not as "good" as people thought they were with the distorted recordings, or was it just that people prefer to hear an altered version?
I'll see if I can scratch up who has done it. It had nothing to do with the performers at all. a totally neutral mic was made, and everyone hated the sound. which makes sense really. its the same reason why a little reverb sweetens up vocals on a recording. doesnt matter if its natural from a cathedral, or synthetic from a machine, it just sounds better. certain frequencies are brought out. cathedrals really emphasize the low rich end in mens voices, while it tames a sometimes shreeky soprano. if you put that same choir in a "dry" room, its just not as enjoyable.

anyway, men typically like a little bump in the low freq when they record. it just sounds better. and certain mics are voiced that way for that reason. its why I love the shure beta 87. lol. great vocal mic.

there are also things like "proximity effect" on a mic, which brings out or tames even more frequencies. whew.. aint it crazy. anyway, i'll see If I can find some stats on those mics.
post #19 of 38
Reproducing audio quite accurately is possible. However, it requires two extremely unconvenient things :
-Being in an anechoic room.
-Having a listening position fixed with an accuracy better than one centimeter.

I've read somewhere than in a usual listening room, 70 % of the acoustic intensity comes from wall reflexions, and 30 % only in straight line from the speakers.

This is consistent with a stunning experiment that anyone with an average microphone can do.
First, set the microphone just in front of the speaker. Something like 20 cm away (10"). Play some music while the microphone is recording. The recording quality has no importance. You can record with a laptop. The microphone should be better than the one coming with cheap soundcards, though.

Listen to the result through you hifi. According to the speakers and microphone quality, it usually sounds quite bad.

Now, set the microphone at your usual listening position, record again, and listen to the result...

Usually, the result is so unbelievably bad, so incredibly different from the previous, that the only sensible conclusion is that the microphone was broken, or just good for a telephone. That's why the first recording, in front of the speakers, is necessary, in order to get a comparison.

The difference between the two is just the sound of your room ! This sound is completely corrected, unconciously, by our brain. We need a microphone in order to record it and listen to it (in the room again).

This was an eye-opening experiment for me. The 70/30 figure for the room/speakers influence looks then perfectly sensible.

Back to the topic, there is something that can't be corrected in a room, from an accuracy point of view : the reverberation.
When a speaker plays a transient sound, like a drum hit, it bounces on the walls and we hear it several times, nearly at the same time, instead of one time. No equalizer can correct this and make us hear only one hit from our listening position.

The other main parameter, resonant frequencies, can be equalized, but it is so much sensitive to the positions of the speakers and of the listener in the room, that it only works for one very accurate listening position. Just lay back in your armchair, and you need to calibrate the equalizer again for this different position !

These are the main reasons that prevent sound accuracy on a stereo system.

There are other factors, more complicated, but very interesting. The stereo imaging is one.
From the phase point of view, one first problem is that sounds coming from the right speaker hit the right ear first, and the left ear immediately after, with a small delay. The original acoustic sound did not necessarily have this behaviour. This may be partially corrected with digital processors, using phase cancellation. But room reverberation limits the efficiency of this method. And it also requires a perfectly fixed listening position.
From the amplitude point of view, the wave front hits our ear from a given direction, which causes characteristics attenuation in the spectrum transmitted in our ear canal, called "combing". Our brain can identify a given comb pattern and find the original direction of the wave front that produced it. This is a limitation that is practically impossible to overcome with headphones, except by rotating the diaphragm, like on the AKG K-1000.

These factors have led to the usual equilateral stereo configuration. Speakers must be in front of the listener, like performers were supposed to be. This is an artificial way of recreating a standard stereo imaging, not necessarily similar to the original one. For example if you listen to the recording of a street parade, with instruments playing completely to the left, and some completely to the right.

In conclusion, scientific measurments about sound fidelity are more often seen for room optimisation and speaker equalisation. The fidelity of CD players and amplifiers to the original signal is so accurate, in comparison, that measuring and adjusting them would be a waste of efforts.
post #20 of 38
Quote:
Originally Posted by evilking View Post
I think (correct me if I'm wrong) the problem is objectively recording sound. Even though sound waves follow fundamental mathematical and physical laws, there's no way to perfectly capture them in any way. All microphones are non-perfect, they're subjectively equalised and they have physical limitations, so all recordings are fundamentally flawed.
If you're being sufficiently anal - not really.

Take an instrument that doesn't produce low frequencies - a flute, for example. Play it in an anechoic chamber and record with with a high dynamic range calibrated microphone, such as one of those modified WM61 capsules that will remain linear to over 115dB. Run this sound through a top-quality microphone pre-amp, and record at 24bit/96khz through the best ADC you can find. Play back the recording in the same anechoic chamber on a high dynamic range speaker with minimal distortion and frequency flat within 0.5dB from 40hz-16khz.

It might be possible to tell the difference, but it would not be easy.
post #21 of 38
Quote:
Originally Posted by Spasticteapot View Post
If you're being sufficiently anal - not really.

Take an instrument that doesn't produce low frequencies - a flute, for example. Play it in an anechoic chamber and record with with a high dynamic range calibrated microphone, such as one of those modified WM61 capsules that will remain linear to over 115dB. Run this sound through a top-quality microphone pre-amp, and record at 24bit/96khz through the best ADC you can find. Play back the recording in the same anechoic chamber on a high dynamic range speaker with minimal distortion and frequency flat within 0.5dB from 40hz-16khz.

It might be possible to tell the difference, but it would not be easy.
Interesting. A couple of things occur to me. First the microphone has to get the exact same signal pattern that the listener's ears get, even in a chamber with no reflections is this possible without putting the microphone inside the listener's ear ?

Then the speakers have to propogate the sound in the exact same pattern as the flutist did , but stereo speakers are normally deliberately set up to create an image center and forward of the listener so there is a crossing of the two channels which you do not get with the flutist, but if the spekers did not cross it would be obvious that there were two separate sound sources. Would you not have to use one unidirectional speaker rather than 2 ?
post #22 of 38
The microphone must get the signal pattern as it travels without any head, body, shoulders or... microphone in its path.

Then, a speaker must recreate it in the same way.

In both cases, shoulders, head and ears should affect it the same way.
post #23 of 38
Quote:
Originally Posted by Pio2001 View Post
The microphone must get the signal pattern as it travels without any head, body, shoulders or... microphone in its path.

Then, a speaker must recreate it in the same way.

In both cases, shoulders, head and ears should affect it the same way.
The HRTF is specific to the angle the speakers are at. If the instrument being recorded was actually supposed to be 90 degrees to the left of the listener, then the wrong stereo image will be produced by even ideal mics, rooms and speakers.

It's not possible to recreate the original recording (including spatial information) to any given listener using the recording method you described (although it is possible with other methods).

BTW aren't we talking about headphones here?
post #24 of 38
I'm sure many of you know this already but I figured I'd point it out. My dad told me that on more than one occasion, while going to see a symphony or orchestra, they were making a live recording of it. To do this, they actually brought out a mannequin head which had two microphones placed at the canal point of each ear. This helped to simulate and record true stereo sound. Of course this doesn't take into account a whole variety of other variables but it seems like a good way to do it. Now I'm sure nowadays they have more "sophisticated" methods for live recordings but I figured I'd toss that out there.

One other thing to take into account in an attempt at "perfect sound reproduction" is Timbre. Which is basically the coloring that other people were talking about. In that link wikipedia mentions:

Quote:
The American Standards Association defines timbre as "[...] that attribute of sensation in terms of which a listener can judge that two sounds having the same loudness and pitch are dissimilar".
There are so many variables when it comes to audio (especially when it's pushed through a mile of wiring and amplified and EQ'd and digitized and then back to analogue....) I would say yes, it's possible. If NASA needed a sound to be identically reproduced they could get it done. Can we, the home enthusiast, recreate exactly what each artist in different studios recorded with different equipment? I highly doubt it. Like those before me have said:

Make it sound the way you want to hear it sound. Nothing else matters.
post #25 of 38
Quote:
Originally Posted by Inquisitor View Post
they actually brought out a mannequin head which had two microphones placed at the canal point of each ear.
This method should work if the recording is played back through earphones, except for the earphone - eardrum resonance, that doesn't exist in the original setup.
post #26 of 38
I think a company should develop the most transparent audio equipment ever, and have it be used as an industry standard, so there is one less variable and we as audio enthusiasts can be one step closer to knowing that it may be possible to be able to hear exactly what the recording was supposed to sound like.

This also makes everyone's "personal sound perception" a moot point, because if it's all based on one standard piece of equipment, anyone that can match that sound will still hear that sound accurately - they'll just perceive it differently. Just like at a live show. Does the fact that everyone hears it differently mean live is not accurate?

Just my thoughts.




Also, FIGHT THE LOUDNESS WARS!

Thank you.
post #27 of 38
Quote:
Originally Posted by i_don't_know View Post
I think a company should develop the most transparent audio equipment ever, and have it be used as an industry standard, so there is one less variable and we as audio enthusiasts can be one step closer to knowing that it may be possible to be able to hear exactly what the recording was supposed to sound like.
That is a good idea. It would have to have an utterly flat frequency response from 10hz to 20hz and be capable of level ratios of say 65,000 to 1 and have noise that is below audibility, say -100db , simlarly it would need to have distortion levels of below -100db to be inaudible also speed deviation so low that nobody even bothers even measuring it. Surely this is Science Fiction though...
post #28 of 38
The same reason why some people like japanese food but others prefer a pizza. We're not clones of each other.
post #29 of 38
I think this is not a technical issue, but a philosophical one. Who is to set the ground truth for "accurate sound?"

We can all agree on a very well-specified technical definition of the color blue (say, electromagnetic radiation with a wavelength of 460 nm). You and I can look at the same 460 nm blue and agree that it is a true blue. Everyone can agree that a meter can register a more accurate assessment of light wavelength than a human can distinguish. Yet, if someone asks you "describe the color blue" what do you say? How can you really be sure that your perfect blue is the same as their perfect blue? How can either of you convince the other that 460 nm blue is the pinnacle of blues?

I see sound accuracy in the same light (ooh, bad pun!). Meters can out-resolve any human, so humans say "oh, the meter is lacking some mojo that my golden ears and brain have." I disagree. Meters convert one physical quantity into another; there is no meter to translate a physical quantity into an objective truth.

Asking "why can't a subjective thing be defined, measured, and reproduced in objective ways" is like asking "what happens when an unstoppable force meets an immovable object." Can't happen. The assumptions in one violate the reality of the other.
post #30 of 38
I disagree. You are comparing reproduction of sound with production of color. The right analogy would be either comparing production of both, thus asking "is this sound perfect", listening to a musician, or comparing reproduction of both, thus asking "are these two blue the same ?"

The problem of sound reproduction is completely technical. There are just two major difficulties : first, the means required to perform accurate sound reproduction are far beyond the normal use of a home stereo system, and include room acoustics and must take into account the listener's position.
2-channels stereo implies that the listener is sitting still. If the listener moves, we need multitrack recording, one speaker per original instrument, that move exactly like the original (e.g. the speaker playing an opera singer will have to walk and rotate exactly like the singer did during the recording) plus extra speakers to simulate exactly the reverberation of the recording location.

Second, since the late 70s, a new paradigm has shifted the home high fidelity from the professionnal one (used in theatres, for example) : measurments have no correlation with listening experience. This paradigm have vastly hindered the development of consumer hifi. Now, we can see that much more effort are put into power cables than into, say, equalisation.
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