Live venue acoustics have similarities with smaller room acoustics but the real success in treating the live venue acoustics is understanding the differences between small and large rooms. Small room acoustics focus on low-frequency issues. Low-frequency waves of energy that are 30′ and 40′ long never fit in a small room. They usually fit in large venues. Large rooms that offer live venue acoustics must focus on the reflections from all the wall surfaces. The accumulation and summation of all of these reflections are termed reverberation. Reverberation is room distortion and reverberation room distortion interferes with speech and music. The smaller the room the more low-frequency issues we have to contend with. The larger the room the more focus must be on the reflections or reverberation time management. Live venue acoustics must take all of these variables into consideration. The larger the room the larger the surface areas are and the more issues we have with the reflections from the wall surfaces.

Reverberation Calculation: http://hyperphysics.phy-astr.gsu.edu/hbase/Acoustic/revtim.html

Reverberation Treatment

When you examine a large room and the live venue acoustics that must be associated with large rooms, we must look at six surface areas. We have the floor, ceiling, and four sidewalls. All of these six surfaces each contribute 17% to the overall acoustic issues within any live venue acoustics arena. Since each surface area is contributing to the total issue, we must address each surface area individually. The chosen method of treatment is absorption. Let’s start with the floor. The floor has good proper absorption on it by definition. Human beings are on the floor watching the performance. Human beings are sound absorbers since we are really just bags filled with water. Some are larger bags than others and thus provide more sound absorption than others. On average a human being has the absorption coefficient of around 12 square feet of 1/2″ carpet with a 1/2″‘ pad. Large venues can have thousands of people sitting or standing on the floor. With all of this “carpet”, our floor surface area treatment requirements are met.

Rate and Level of Absorption

To manage the reflections from the sound source to the walls and then reflected back into the audience we use absorption. Since the distances are large, we must use the most economical of the treatment types to deal with high Rt-60 (reverberation) times. Absorption is the chosen technology. The best absorption material is open-celled foam. You can use an open-celled foam that was specifically designed for music and voice. It will have the smooth absorption response curve which will prevent the room sounding too small a phenomenon that occurs when too much absorption is used along with an improper rate and level of absorption to address specific absorption issues that music and voice require. There are two main types of open-celled foam. There is one type that is designed to absorb as much energy per square foot as its design will permit. The other foam type is like our foam which was specifically designed for music and voice. Its linear absorption rate and the level go a long way to bring out every detail in voice and music. Music and voice are different.

Acoustic Foam Performance Graph

Speech Intelligibility Index

There is an index that deals with speech and the hearing of each word in a ten-word sentence. If you hear 6 out of 10 words you have an SII of 60. Our goal is 8 out of every 10 words. An SII of 90 is recording studio quality. Our goal with speech intelligibility indexes is to use enough absorption to lower the negative impact of reflections from the live venue acoustic surface areas. Any live venue acoustics must take into consideration to speech intelligibility indexes. The acoustical goal with Rt-60 time management is first and foremost speech intelligibility. We need to reduce the reflected energy from the four walls and ceiling down into a range where we here more words and less room sound. It’s the words and music that connects us emotionally to them. The more words we hear and the more music we hear, the more emotional connectivity to this source we experience.

Live Venue Acoustics Treatment

We have to use absorption to reduce the strength of the reflections in live venue acoustics to increase speech intelligibility levels. We must cover large surface areas in any live room acoustic treatment types selected. On average, we must cover 70% of offending surface areas. We must use absorption technology that has the proper rates and levels of absorption to match our middle and high-frequency reverberation times. Music and voice are different. They both require a smooth rate and level of absorption to treat correctly. There can be no spatial irregularities in the absorption coefficients of the material type we use. The level of absorption must begin at 100 Hz. and go through 6,500 Hz. This frequency range management is a must. Additional higher frequency absorption types may be required above 6,5K but this is a must-start and treat frequency range.

Nick-Ceiling Wideshot

Open Celled Foam

The most effective and economical way to cover large surface areas is to use open-celled foam. Open celled foam has a predictable rate and level of absorption. It also is manufactured in large sheet sizes. Our open-celled foam comes in 55″ x 75″ sheets that can be easily installed. It is lightweight and can be installed easily at higher heights which usually exist in live venue acoustics. You must use a lightweight, high performing technology when you are working with larger ceiling heights. Installing material at those heights gets more problematic the higher the ceiling heights. Different color options are available and fabric facings can be managed to match any existing decor.

Studio Pro Foam: https://acousticfields.com/product/acoustic-foam/

About Us At Acoustic Fields: https://acousticfields.com/about/

Dennis Foley

Author Dennis Foley

I am an acoustic engineer with over 30 years’ experience in the business. My technology has been used in Electric Lady Land Studios, Sony Music of New York, Cello Music and Films founded by Mark Levinson, and Saltmines Studios in Mesa, Arizona, along with hundreds of others.

More posts by Dennis Foley

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