Concert Hall Acoustics

Sunset Center, Carmel, California

This hall, a performance venue for several classical music groups is scheduled for renovation starting in 2001. Located in Carmel California, the renovation must follow some strict constraints for preserving the style of the current architecture of both the inside of the hall and the outside of the building.

This study of the acoustics of the hall starts with several cases of the hall in its current configuration:

Case 1: single performer at the center of the stage

Case 2: single performer at the left of the stage (as seen by the audience)

Case 3: multiple performers representing an orchestra on stage

For each case we show the distribution of several acoustical quantities throughout the hall and on stage. We do not show all quantities collected (i.e. Early Decay Time (EDT), Reverberation Time (T30), Clarity (C80), Definition (D50), Loudness (SPL), Envelopment (LF), and Speech Intelligibility (SI)) due to the potential for information overload. Instead we show a sample of results that illustrate important acoustical observations for that case.

For each case we also show the details of the sound at selected seats within the hall. This includes the reflectogram or distribution of “echos” arriving at the seat during the early sound. A near continuous set of spikes represents a full continuous sound (very desirable) whereas a few widely separated sets of spikes would sound thin and perhaps “echoey”.

We also show a “sound rose” at the seat showing it the sound comes from a few locations or many. A “fuller” sound rose implies a greater sense of envelopment for the listener, a very desirable characteristic.

Comparing results for Cases 1 and 2 show the sensitivity of the hall to performer locations. For seats where the hall responds quite differently for these two cases, an ensemble performance will not sound well balanced and perhaps not well sychronized. A third case is included with several sound sources covering the stage.

A similar set of studies were then done for the hall in the same configuration, but with the ceiling material changed from wood to plaster:

Case 1 (Plaster Ceiling): single performer at the center of the stage

Case 2 (Plaster Ceiling): single performer at the left of the stage

Case 3 (Plaster Ceiling): multiple performers (i.e. an orchestra on stage)

A similar set of studies were then done for the hall in a hypothetical configuration close to the current proposal for the hall’s renovation:

Case A: single performer at the center of the stage

Case B: single performer at the left of the stage (as seen by the audience)

Case C: multiple performers representing an orchestra on stage

Brief Summary of Conclusions

Results for these nine cases show the impact of modifying the proscenium arch, making the aches spanning the width of the hall 90% transparent, changing the shell surrounding the performers, and changing the material properties of the ceiling.

• The current configuration of the hall has too short a decay time (the sound disappears too quickly). This agrees with the performers’ and audience’s impression of the hall being very “dry”.

• Changing the ceiling material of the current hall from wood to plaster, creates a much livelier hall.

• The sound shadows caused by the current proscenium arch and the arch beams spanning the width of the hall create significant blend and synchronization problems for more than half the hall in it’s current configuration. The changes we modeled for the Renovated Hall (Layout A) improved on this problem significantly for nearly the entire hall.

• Both the current hall and the renovated one we modeled have poor lateral reflections which result in a poor sense of envelopment. We believe this is due to the vaulted ceiling. The effect actually gets worse for the renovated hall. There are several approaches to deal with this. Also, we expect the results would look somewhat better with a balcony added to the model (unfortunately, we did not include a balcony in these studies).

• Plans for a sophisticated speaker system to support the sound of the hall should help the lateral reflections mentioned in the previous bullet. This system is designed to make the hall appear to have a larger volume and thus make the hall sound livelier.

Disclaimer: These results are based on models that are similar to the current Sunset Center Hall and its proposed renovation not a precise reproduction of either the hall layout nor its material properties. Therefore the results are only illustrative of the performance of the current Sunset Hall and a proposed renovation of it.