Here is an outline in layman’s terms of acoustical problems in gymnasiums:

1) All the surfaces are hard, including the floor

Most other spaces, if you think about it, at least have some carpet on the floor or a drop tile (absorptive) ceiling.  In addition gyms walls are generally all cement block to endure the use of sports events.

While drywall is still very reflective, cement is sonically more reflective at most frequencies.

2) There is little or no seating. Even a hard room with padded seats would at least break up some sound waves as they travel about the room.

3) Any adjacent stage area contributes to amplification of reflective sound energy.

4) Open HVAC system designs are loud. Most gyms have the roof top units simply mounted on top of the roof without any consideration of decoupling them from the structure. Any vibration from the furnace / air conditioning unit is transmitted directly to the roof decking. When the unit starts up it is often very noticeable.

All this means a large volume room typically with no absorptive surfaces. Gyms therefore, have lots of echoes or high-powered reflections, a long reverb time and high power standing waves that are in the low frequency domain. Any combination of these issues means a loud room with poor intelligibility for speech. Any musical presentation is muddy and hard to make clear, even with good sound equipment.

Acoustical Fundamentals

The acoustical environment of a room described above needs attention in the right areas. If hard surfaces are reflecting dominant frequencies, they need to be reduced. The offending frequencies need to be determined to develop a treatment best suited this space.

Fundamental frequencies are in the low / bass frequency range. They are large and powerful. As a result they also excite adjacent, upper harmonic frequencies. If there are issues in these frequency areas (e.g 200 or 500 Hz) you need to break them down and reduce their power by the correct form of treatment in the appropriate manner.

Many rooms like this have some form of absorption or sound panels. While this will be helpful to reduce the mid and upper harmonic frequencies, the lower, more powerful fundamental frequencies remain untouched. This will result is a room that is boomy or muddy and still loud and basically unintelligible.

Without dealing with the offending powerful, low frequencies the space will not have the ability to carry on any clear communication. This is regardless of how much absorbing material is installed. In fact, adding too much absorption can make a room worse since speech intelligibility and pronunciation of consonants resides all the higher frequency range. Hence this removes needed clarity.

Absorption can be in many forms but it is usually a flat panel that is made of a variety possible materials that capture air /sound energy. This energy is then converted into heat. The amount of energy decrease (attenuation) is determined by the size, density and thickness of the panel. If an air space is placed behind the panel, it will be effective to a lower frequency range.

Absorption panels are only effective for the space they cover. If you have a wall surface causing reflection problems, you generally have to cover the width of the entire wall and the required height causing the issue.

An Intriguing factor that determines the rate of absorption is the angle of the sound impacting the acoustical panel.  At 90 degrees you will most likely get the performance the flat panel is rated for.  At greater angles you will get much more performance which results in more absorption than what was specified.  This always results in an over dampened room that not only reduces the noise but it makes speech more difficult to hear.  For example a two inch (5 cm) panel may give you 6dB of performance (reduction) at 4000 hertz at 90 degrees of sound impact. In comparison at 45 degrees in and 135 degrees out, you will get 6dB at 2000 hertz.  These specifications may sound great, but this can over absorb the 2000 - 4000 range when the problem in the room is actually excessive energy at 500 hertz. To attenuate into the 500 Hz range you would need panels two feet (60 cm) thick.

Diffusion doesn't just absorb sound waves but it also scatters them. This redirects problem reflections and minimizes them, while at the same time leaving a natural sound in the space. This occurs at all frequencies, especially in the bass, fundamental frequency range, which is harder to control and reduce or attenuate.

There are numerous forms of diffusion available and most are more costly then absorption. CS Acoustics uses a diffusion system that uses multiple units in tandem with each other and the surrounding surface. As a result we are able to use a much smaller surface area foot print than absorption panels and yield a greater amount of reduction at a competitive price.

Assessing the Intended Use

If you only use your gym for sports perhaps this is not a concern however communication of game plans or other instructions must be given with a loud voice of or an even louder PA. Just because the volume is increased it doesn't mean hearing clarity is improved.

For any sports participant who struggles with hearing or sensory issues (e.g. Autism Spectrum or Central Auditory Processing, etc) this experience is frustrating, humiliating and anything but desirable and encouraging. Behavioral issues increase, especially in individuals exhibiting ADHD.

If you use a space such as this for plays, meetings or worship, it will be most detrimental for any intended form of communication. The ambient level (loudness) alone is fatiguing, distracting and agitating. For those hard of hearing, often more then one word out of five is not understood. Music can be muddy, unbalanced and distorted even with appropriate sound equipment with competent operators.

Impact of Acoustical Treatment

Balanced acoustics in a space of this design allows for more flexible use over the lifespan of the building. A gym could now be used for many other types of events including drama, meetings, meals, etc as referred to above. A quieter gym can also produce better athletes through more productive training times with less distraction and behavioral issues.

We accomplish this by applying the correct amount of diffusion in addition to the required absorption. The result is typically a room that is 10 - 20 dB quieter and speech is so clear that you can hear a conversation from one end of the room to the other!

For more detail on our concepts and how we can help your situation please contact us!

Case Study: Creekside Church - Waterloo, ON

Type of room: Gymnatorium

Size: Seats 650

Creekside Church’s worship format incorporates contemporary worship with a full band. Sermons and other speech parts of the service are generally amplified through omni-directional headset microphones. The Sunday services are repeated four times as the space is not large enough to accommodate everyone in one or two services.

Before acoustically treating this space 13 audible reflections impeded clarity and amplified the ambient levels. When the air conditioning or heating came on it was very noticeable and shrunk the available window of sound to be heard over top of the noise floor. Any kind of detailed presentation was difficult to comprehend.

Low frequency energy, particularly during the music presentation was muddy, distorted and lacking in definition, even after adding a sub woofer. The stage area was surrounded by solid block walls and had been partially treated with a variety of 2” thick panels made with insulation covered in fabric.

Part of our acoustical design and treatment was to deal with the stage area. By adding the variously sized diffusers around the perimeter of the stage, the low frequency energy was better controlled and the energy radiating from the stage into gym / congregational area was significantly reduced.

The balance of the room also had diffusers installed on the walls. This worked well in tandem with the Acoustiblock (slotted blocks designed for acoustical purposes). Our telescopic diffuser system was installed on the side walls. These are dropped down during worship presentation times and retracted during sports use.

Part of the worship service design incorporated the absorption co-efficient of the 600 padded chairs. The result of this treatment was ambient level reduction of 20 dB. Also the low frequency / bass energy was greatly more defined giving an increase in bass energy of four times. Speech is markedly clearer and the live band can be mixed at a lower level with more clarity as the offending reflections are now eliminated.

If you have a contemporary worship service, with a live drummer, we can help balance the levels of various instruments in the band and bring out more speech clarity while reducing the overall sound level, as has been experienced at Creekside Church.