control room acoustics

F

frequency_

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hi, i turning two rooms into a home studio, one of my problems is that the control room is almost square (L:3.75m, W:3.68m, H:2.70m) and there will be problem with standing waves. I m placing a difuser on the back wall and i m not making the ceiling completely straight, i m giving it a few degrees, but will that be enough to sort the standing waves problem?
 
thanx

thanks for that i read the web page, the room though has a flat reverberation time of around 0.4 seconds, would bass traps cause a reduction on reverberation at low frequencies? if so.. do you think would it be better to have standing waves or poor low frequency reverberation responce? thanx
 
would it be better to have standing waves or poor low frequency reverberation responce?
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They would seem to be one and the same. With bass traps you smooth out the low frequency room response by removing the ability of waves to become "standing waves". Modal decay rates vary in small rooms, and characteristicly gives uneven response. This means resonances occur at wavelengths comparable to the rooms dimensions and multiples of. Those are standing waves. BTW, ever heard a standing wave? I've often wondered how one can hear a wave that isn't moving :p :confused: Anyway, from my understanding, when a "standing wave" becomes a "traveling wave", there can be no resonance. If my understanding of this concept is correct, this means if a resistance absorber, such as a "superchunk" of rigid fiberglass is placed where these low frequency resonances occur, there is very little reflection, therefore no ability to become a standing wave. I think. Hmmm, did I tell you anything?
Ethan, does that make sense? Or am I misunderstanding something here.
 
Rick,

> Ethan, does that make sense? <

Sure.

In the larger picture, all room acoustic problems are caused by reflections. So if you reduce the reflections you reduce the problems, whether they're peaks and nulls, flutter echo, excess ambience, modal ringing, early reflections, or all of the above at once (which is usually the case).

--Ethan
 
Hey Ethan, thanks a lot bud. Maybe this ole skull has "absorbed" something afterall. :D And then again, maybe I said the blindingly obvious :confused: :eek: :rolleyes: :o Woudn't be the first time. You see, I have this affliction called...babblespeak:p

Out of all things acoustical I STILL don't understand though. is distance. I live up on a forested hill. When I lay in bed at night, I can hear sounds down in the valley below I listen for cues that will answer my question which is..what is it about sound, that you can tell the approximate distance, and if its stationary or moving, EVEN if you are seperated from it by an enclosure. This is what baffles me. When I'm laying there, I can hear a car, or a dog, or boat etc., from various distances. I hear NO echos, or any reflection phenomena to account for the "distance" quality I hear, which in the room, even seems more bizaar. SUPPOSEDLY, When a DIRECT sound(wave) reachs my ears, there is a short delay between one ear and the other, which is because of the speed of sound. This gives the brain clues to DIRECTION, no? But what clues does the brain decipher that account for distance. Being in a valley, there are certain sounds that DO echo. REALLY LOUD :eek: Like thunder. Or a ship in the slough down below. and an occasional plane. But moving traffic or a car starting up have lower amplitude. And thats the other thing. Even very quiet sounds, still have a "distance" quality. In fact, this is what bothers me. When you "hear" sound, your ears are picking up vibrations in the air, DIRECTLY at the physical point in space where the vibrations are passing your ear canal. Then what is it that tells you the sound is at a distance, and what that distance is approximately. Even outdoors, when a person speaks to you 10 feet away, it sounds different than when he is 5 feet away but speaking at a relatively lower SPL. Thats why I'm not talking about amplitude, because if your ears detect two sounds that are 1000 feet apart' yet produce the same amplitude level when exiciteing your ear drums, why can you tell the distance. I've stood in the backyard and listened to ambient sound with my eyes closed, and could pick out things very distant, while very soft music was playing in the background 20' away. Some sounds matched the amplitude of the radio. Yet I could hear the distance.In an enclosure such as my bedroom, this "quality" also passes through the wall. yet I hear no local reflections, or "comb filtering" type effects off the hills that surround my property outdoors So, anyone got a clue to give me. :D BTW, it would seem your OWN voice has something of a "distance" standard the mind uses as a "calibration" or comparison to, since it is the closest to your eardrum, no? :confused: Anyway, just one of my meandering "curiositys". :D
Thanks again Ethan. :)
fitZ
 
Hey Ethan, here is another "curiosity".
Take a controll room. Define its purpose. For audio recording, it would seem the highest priority for a "tracking" control room, is CONTROL ROOM ACOUSTICS, whereby the sound occuring in the studio is re-produced in the contol room WITHOUT the control room acoustics MASKING comb filter effects in the studio, NO? This means being ABLE to hear comb filtering IN the studio, over the monitors, no? However, it would also seem the the second priority would be to judge this "studio sound", within the context of "translation", which means you can only "subjectively" listen to the "studio sound" as the control room should ONLY allow for direct sound from the monitors. The second you allow the control room acoustics to "approximate" what it should sound like on a "translation" system, then you have defeated the first criteria, no? Hmmm...(sigh) :confused:(not really but sometimes)
fitZ
 
Rick,

> what is it about sound, that you can tell the approximate distance, and if its stationary or moving, EVEN if you are seperated from it by an enclosure. <

You may be over-thinking this. One of the biggest things that happens with distance is a loss of high frequencies, not to mention loss of volume. Even through a wall you can hear that a passing car has less mids and highs. My house is 100 feet or so from the road, and I can easily hear the difference between a truck passing by on the street and a truck coming up my driveway.

> This means being ABLE to hear comb filtering IN the studio, over the monitors, no? <

Of course. But as long as the control room monitoring is clear and free of those artifacts, you'll be able to hear comb filtering due to the microphones or performer being near a reflective boundary.

--Ethan
 
Hello Ethan. Thanks for the try, but I can't really explain what it is I am asking.
One more time. When you hear a sound source that is say a 1/2 mile away, its actual location is where you hear the sound, not at your ear drum, even though you don't hear the sound untill the wavefront reaches and excites your eardrum. If your ears are only excited by the soundwave, then how come it SOUNDS so far away. Like ears have depth perception or something. :confused: :p
Anyway, don't try to answer. I know what I hear, but I don't have words to ask the right questions yet. Thanks again.
 
Rick,

> Like ears have depth perception or something. <

I promise you there's no magical as-yet-undiscovered property of hearing. We localize sounds by their volume, high frequency content, reflection timing, and phase / timing / volume differences between left and right ear arrival. Maybe you live in a valley and unconsciously sense a delayed bounce off a mountain side that's not too far away? Whatever, it's got to be one of those things I mentioned, or something related.

--Ethan
 
I promise you there's no magical as-yet-undiscovered property of hearing.
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Of course not. :D Its just that I haven't read anything that describes why you hear distant sound sources WHERE they are at. At first glance it seems simple. But when you think about it, how does the brain decipher sounds that are close, and sounds that are distant. What happens to a sound wave as it travels to your ears over a long distance. I mean, imagine this. IF a DIRECT wave reaches your ear from a 1/2 mile away, there is a time delay between when it is produced and your ear detects the disturbance in air, right. The ONLY thing that has happened is the inverse square law. Yet, the sound STILL is heard at its SOURCE LOCATION. Anyway, thanks again. I just read all I could find on the net yesterday, and NOTHING is mentioned WHY we hear the sound at the LOCATION, not at the eardrum. Even in an anachoic chamber.

Try this. Sit in front of a speaker about 4 feet away. Turn the source volume of SPEECH down to barely detectable. Close your eyes and COVER one ear. You will still hear the source where it is. Now, while you have your eyes still closed, and your ear still covered, have someone move the speaker. You STILL will detect the distance as you hear the LOCATION. No time delays between ears. You can actually walk to the source as a function of distance.
To some, this may seem.....well, ludicrous as well as obvious. But listen to a car a long distance away, and tell me WHY you hear the sound AT ITS LOCATION. Not simply soundwaves reaching your ears after traveling to them. There is something not quite right. At least to everything I have read about sound.
ou may be over-thinking this. One of the biggest things that happens with distance is a loss of high frequencies
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Yes, but unless you could hear the difference between the sound AT THE SOUCE, and AT YOUR LOCATION, you wouldn't know anyway, so how is that a cue?
 
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I did a bit of movie sound effects work and the stuff Ethan described are the usual clues that your brain uses to figure distance. You are forgetting in your speaker experiment that if the voice was recorded from 20ft away and you listened to the speakers in a completely dead room you might guess completely wrong as to the location of the speaker.

Different outdoor environments can trick your ears. Sounds over water or snow seem a lot closer then they do if you hear them in a canyon or downtown area because the direct sound to ambient sound ratio is much higher.
 
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