Analyzing Concert Hall Acoustics

The acoustic environment of a concert hall is critical to the experience of performers and audience members alike. Effective acoustic measurement and analysis are essential for ensuring optimal sound quality.

This article presents a detailed case study conducted at a historic concert hall in Switzerland using our state-of-the-art Sound Scanner technology. The analysis demonstrates the capabilities of the Sound Scanner and provides insights into understanding sound propagation in large rooms and greatly reducing troubleshooting time.

 

Description of Use Case

Herrmann Partner AG, a prominent acoustic consultancy, engaged our services to evaluate the insights gained by visualizing sound propagation inside a historic concert hall in Switzerland.

Specifically, they were interested in measuring and analyzing sound paths, reflections, and reverberation within the stage to better understand potential recommendations for acoustic treatment.

During concerts, musicians from the orchestra complained about an uneven sound distribution across the stage. Musicians positioned on the left side of the stage perceived the sound coming from the instruments on the right side as excessively loud. They also reported a significant delay and echo from these instruments.

 

The identified problems were: (1) too high loudness and (2) delayed perception

 

To address these concerns, we utilized the Sound Scanner P132, which features a 132 cm scan diameter and operates within a frequency range of 250 Hz to 6.1 kHz. This model is ideal for applications involving large room acoustics and building acoustics, given its manageable size while offering an appropriate frequency response. 

 

 

Measurement and Analysis Process

The Sound Scanner was strategically positioned in various locations within the concert hall to capture a comprehensive acoustic profile. The process involved rotating the sensor to acquire periodic pulses, transferring data to a mobile device and cloud for processing, and visualizing the results.

We began by positioning an omnidirectional sound source on the right side of the stage, where the problematic instruments were located. The Sound Scanner was placed on the left side, facing the source. An impulse signal was emitted repeatedly by the source, and after 10 seconds of integration, the software was able to generate a complete impulse response and a decay signal.

 

The Sound Scanner was positioned on the left side of the stage and the omnidirectional sound source on the right side.

 

 

Three specific sections of this signal were of particular interest:

 

1. Direct Sound: The first peak in the signal, occurring within the initial milliseconds, represents the direct sound emitted by the source. 
2. Primary Reflections: These reflections occur within 20-50 milliseconds after the initial impulse (depending on the literature). They significantly influence the perception of loudness but are not critical for the perception of delay
3. Late Reflections: Reflections occurring between 50-100 milliseconds after the initial impulse are crucial in terms of delay perception. These reflections were found to be the main contributors to the echo effect perceived by the musicians.

 

Impulse Response Report on Acoutect App.

 

Analysis of Results and Solutions

The acoustic images corresponding to each time interval provided a clear visualization of the sound paths within the concert hall.

 

 

1. When analyzing the 0-5 ms interval, the direct sound from the loudspeaker was perfectly localized;
2. Primary reflections, which occurred 20-50 ms after the initial impulse, were mainly from the side diffuser wall and slightly from the floor and diffuser ceiling;
3. Late reflections, occurring beyond 50 ms, were primarily coming from the untreated upper wall and diffuser ceiling.

 

To address these issues, following solutions were recommended:

1. Sound Absorption: Introducing absorbing material in areas where primary reflections were prominent, such as the side diffuser wall, could reduce the perception of excessive level.
2. Treating Critical Zones: The area between the diffuser wall and the ceiling was identified as a critical zone for improving delay perception. Acoustic treatment, via diffusion and/or absorption is recommended to manage late reflections and reduce the echo effect.
3. Enhancing the Diffuser Ceiling performance: To further mitigate critical reflections, additional acoustic treatments on the diffuser ceiling were suggested. 

 

Conclusions

The measurements performed at the historic concert hall using the Sound Scanner provided valuable insights into the hall’s acoustic profile.

By identifying key reflective areas, the study enabled potential recommendations for acoustic treatment. This case underscores the importance of advanced acoustic measurement technologies in maintaining and improving the sound quality of performance spaces.

For more information on our Sound Scanner technology and how it can benefit your acoustic projects, please contact us.