Night Club

Night clubs can be classified into three groups: The café bar where friends gather for lively conversation; the show club with a stage and nightly performance; and the discotheque that drums the beat for dancing all night long. When it comes to acoustics, the goal is to retain a sense of atmosphere while trying to create an inviting environment that is conducive to conversation. And more often than not, concerns with regards to containing noise to avoid bothering neighbors must be addressed.

The café bar

Hotel cafés, social clubs and sports bars are places designed for patrons to relax, meet with friends and engage in conversations as they watch the game, listen to music or have a snack. On one hand these spaces must provide entertainment to keep single folks engaged while on the other, sound levels must be kept under control so that couples or groups do not end up yelling when trying to converse.

As with most commercial construction, walls tend to be made from highly reflective surfaces such as gypsum board or concrete, mirrors usually grace the area behind the bar and windows invite the passersby to come in. As more and more people fill the bar, the sound level increases, the bartender turns up the football game and next thing you know, the whole room has become a cacophony of noise.

Show clubs add another dimension to the challenge in that they combine the problems associated with communicating around the bar with the added sound from the band's PA system. While the ‘noise' in a café-bar is centered on the voice range, in show bars, the audio system is now delivering full range music and it is a lot louder. As the sound pressure increases, more treatment is usually applied.

As a general rule, the thicker the acoustic panel, the lower frequency it will absorb. This of course is also dependent on the density of the acoustic panel. Low density foam for instance will absorb high frequencies, but is much less efficient at absorbing bass. And because urethane foam is flammable (even when treated with flame retardant), using it in public places can present problems with insurance and legal liability.

The above graph compares three Broadway panels. The 1-inch thick panel is designed for voice showing 100% absorption at the critical 500Hz region. The low profile design makes this a good choice for controlling noise around the bar. The 2-inch and 3-inch panels provide greater attenuation in the low frequency region. These of course will help control bass resonance and are better suited in areas where music is playing.

The Discotheque

What makes the discotheque unique is that these venues are typified by loud music everywhere in the attempt to elevate the energy in the room. Ideally, most of the sound energy should be directed at the dance floor and areas in the periphery would be acoustically treated to enable patrons to converse.

Once again the problem is repeated: As the DJ turns up the beat, the sound pressure in the room elevates to the point where the room is no longer able to naturally dissipate the energy. The threshold is exceeded. The solution: Acoustic panels are mounted on the walls to dissipate the energy by way of a thermo-dynamic transfer whereby sound energy penetrates the minute glass wool inside the panel, causing it to vibrate and generate heat.

As these venues tend to be very bass heavy, they introduce the added problem of uneven bass caused room modes: bass frequencies reflecting off the walls either combine with the sound from the loudspeakers to create hot spots where bass is extra loud or cancel when out of phase, causing the bass to be lacking.

This image shows what happens when bass waves combine when in phase or cancel out when out of phase. Adding bass traps like the Primacoustic MaxTrap or FullTrap can dramatically reduce the resonance inside the room, thus resulting in a more balanced sound throughout the club.

Stopping sound from escaping

In acoustics, managing high frequencies is relatively easy compared to bass. High frequencies have less energy and the shorter wavelengths cause the waves to be directional. This means we can predict where high frequency sound will travel by looking at the dispersion pattern of the PA system's horn and drawing vectors outward. By positioning acoustic panels on hard reflective surfaces, excessive echo and room ambiance is attenuated.

Managing bass in an altogether different matter: bass waves are long, powerful and omni-directional meaning that they go everywhere. This not only makes them more challenging to control inside the room, but containing them is difficult if not impossible. When attempting to control bass from escaping, the first thing to do is to reduce the bass inside the room using bass traps. This will improve the sound of the audio system by reducing hotspots. With less energy in the room to contain, creating barriers becomes a bit easier. The next stage is determining how the bass is escaping. Doors and windows are often a source. These are generally addressed by adding mass to or by adding a second set. In doing so, bass energy must cause the first set of doors to vibrate, which in turn must cause the second set to do the same before the sound can escape. By introducing an air space between the two, you are decoupling the energy. Herein lays the magic to containing sound.

With walls, the trick is to build a heavy inner wall and ‘float it' in front of the outer wall. This is usually done using resilient channel whereby the inner gypsum wall is left to vibrate freely on top of the outer wall. The heavy mass requires lots of bass energy to set it in motion, introducing yet another level of thermo-dynamic energy transfer which results in less energy for the outer wall to contain. Ceiling tiles are also a ready conduit for sound to escape. Light weight tiles do not stop bass, it simply passes straight through which causes the floor above to vibrate. Adding a mass component such as found in Primacoustic ThunderTiles will help a lot. The gypsum mass component employed in the ThunderTiles is first set to vibrate before the sound can reach the upper floor, greatly attenuating the energy. The air space introduced by the drop ceiling naturally decouples the two surfaces and one again, sound is better contained.

It is important to note that bass when driven to extremes can cause the concrete substructure of a building to vibrate. Stopping this type of energy is practically impossible. When analyzing the problem frequencies, you may find that the beams are resonating at a certain frequency and shifting the bass using an EQ can sometimes help.

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Determining Coverage

To determine the coverage, we have created a series of easy-to-use tables that enable you to choose between various degrees of treatment depending on your budget and the desired outcome. Most facilities find that a ‘light' level of treatment provides sufficient sound abatement while keeping the budget in check. If budgets are tight, start with minimal treatment and then add more panels as funds become available.