Room Acoustics Forum by Rives Audio

RE: I am fairly new to this field

83.84.178.82

In Reply to: RE: The room is fairly medium sized posted by hellobla on December 12, 2007 at 08:05:13

Me too, in the sense that I'm currently reading the relevant scientific/technical/psychoacoustic literature.

>I wanted to measure ETC because I thought it would give me an idea of the reflection levels in different parts of the room, early and late reflections, etc. and I would be able to see what degree of treatment I needed here>

The sound field in small rooms consists of direct sound, early reflections and a much diminished reverberation field. All of the early reflections are above thresholds of audibility, but with music none of the reflections is audible individually:

Bech, “Perception of reproduced sound: Audibility of individual reflections in a complete sound field”, Audio Engineering Society preprint 4195 (1996)
Bech, “Timbral aspects of reproduced sound in small rooms II”, J. of the Acoustical Society of America 1996, vol.99, no. 6, p.3539

Late reflections (i.e. reflections >80 ms after direct sound) are of importance in concert halls, they provide listener envelopment, but not in small listening rooms.

Why would you want to treat? Where is the problem? Is it because everybody says that one has to treat his/her listening room? I just finished the draft version of my literature review concerning early reflections and there is no evidence whatsoever that early reflections are a problem and need treatment. On the contrary, the available evidence strongly suggests that reflections are no problem.

Exception: reflections like those from front and back walls result in high interaural cross-correlation, reflections from walls very close to the speakers are possibly below the time window of the precedence effect, both might benefit from treatment, but that’s about it.

Whoever says that reflections are a problem, ask him/her for solid evidence. In the case that you want to read my draft, feel free to contact me off-board.

> As for the freq response, if it is done at different points in the room and averaged, an idea of the resonances that exist in the room would could be observed<

I have not yet read the available literature about standing waves in small rooms, but only those resonances audible at the listening position would be of interest, wouldn’t they?

< But with room measurements, we get actual numerical data of the room which we can alter to solve part of the problem leading to a better sound than without the measurements.>

He who measures assumes a priori that there is a problem. If not, why measure in the first place? I think that this a priori assumption is wrong, however well established it may be in audiophile circles. There is actually not much research about small room acoustics so I wonder what this assumption is being based on.

< The easier way is to attack the room measurements and determine the properties of a room for important places like studios, halls, theatres which will in a general sense improve the sound quality of the space.>

Small rooms and large rooms are different beasts and different acoustical conditions are present. In small rooms you have well separated room modes, in large rooms you don’t. In large rooms the separation is made between early and late reflections at 80 ms, this concept does not fit into small rooms. What will work in concert halls will not necessarily work in small rooms.

Note I’m talking two-channel here, not multi-channel.

Klaus

Follow Ups:

Post a Followup:

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.