7-7 Solving Acoustic Problems

What are the common problems of a poorly designed auditorium?

1) Background Noise

Definition:

Background noise is any sound other than the primary sound being monitored.

Solutions:

- Air ducts linked with sound-absorbing materials

- Bends in duct systems

- Noise diffused at air supply and return points

2) Reverberation Time is Excessive

Definition:

Reverberation time is excessive when it takes too long for the sound to come back to the listener after it has been reflected off the surfaces. It is important to remember that "excessive" is a subjective term which will be different for different people and different venues. For example, the appropriate reverberation time is different for a concert than a lecture.

Solutions:

- Ceilings lowered

- Add absorbing materials (curtains, draperies, carpets, upholstered seats, etc.)

- Add decorative geometric designs to wall to increase absorption

- Add protrusions to the wall to trap the sound energy

3) Inadequate Loudness

Definition:

The sound's loudness is inadequate if there are seats in the hall where listeners have trouble hearing the performance.

Solutions:

- Add reflecting panels to wall and ceiling

4) Echos, Hot Spots, & Dead Spots

Definition:

An echo occurs when a sound is being bounced off a distant surface (the reverberation time is more than 0.1 seconds). A hot spot occurs when the curved walls or domed ceilings focus the area into a single area where maximum reflection occurs. A dead spot is a spot where few waves are being reflected back making the sound dull and faded.

Solutions:

- Make the reflecting surface closer to the sound source

- Increase reflecting panels to wall and ceiling

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