The 2 Second Rule in Sound Control

If you stand in the middle of a room and clap your hands once, invisible sound waves are generated that in turn spread like a pebble wave in a pond, traveling in every direction within the room, at speeds nearing 800 miles an hour.   As the perimeter wall, ceiling and flooring surfaces receive the sound wave signal, the wave is reflected back into the room, heading towards your eardrums.   What your human ear hears is a single sound, the clap of your hands.   But what your human ear is actually hearing, are two distinct sound signals: the original sound and the reflected sound that has first bounced off a perimeter surface and returned to you at near lightning speed.

So what is the 2-second rule in the field of sound control?   It is the measurement of how fast the reflected sound wave can die off inside a room.   The human ear has a threshold level of two seconds or less worth of what is called ambient echo.   If your room is filled with hard reflective surfaces, the echoes will continue to bounce inside the room for up to 10 seconds.   That causes background noise and blurred sound signals.  But if the same room is properly treated with acoustic panels designed to capture and convert the echoes from the space, your echoes will die in under 2 seconds, and clarity to the original sound is restored.   Any room that sounds good to the human ear will have background noise levels under control, and by definition, that means the echoes drop off in under 2 seconds.   Any room that sounds loud, with blurred sound signals, and difficulty in communications, will have echoes that carry on average between 4 and 10 seconds. Whether a loud restaurant, a noisy gym, poor quality sound in an auditorium, a classroom, a sanctuary, a cafeteria, a music studio, or a call center, these rooms all share the same common ingredient of hard reflective surfaces that will bounce echoes, blur sound signals, and cause noise.

Perimeter surfaces in a room will define the length of time it will take for the sound waves to die off in that room.   Brick, block, wood, steel, marble, granite, glass, and metal will all reflect an average of 3-8% of the echoes in a room. Sound panels, on the other hand, can capture and convert up to 80% of the same level of unwanted echo. A good sound consultant will help assist you in determining appropriate coverage amounts of a sound panel system for your room, based on the room’s size, shape, and surface textures prior to the treatment.   The key to the success of a sound panel system, the key to dropping your echoes down under 2.0 seconds, depends on getting your coverage amounts right.   You do not want to undertreat the room, and there are simple formulas that can help you calculate how much sound panel coverage your room needs in order to beat the two-second rule.

Note that some sound panel suppliers will overextend their coverage amounts, working more material into your equation, in an effort to drop your echoes in the room down to 1.5 seconds, or further down to 1.0 seconds.   While there are times when this makes sense, and this can double your cost for your sound panel treatment, in the case where premium sound quality is required for voice clarity in a lecture hall, for example, the reality is that the majority of sound panel treatments do just fine dropping the echoes to 2.0 seconds.   Customers are encouraged to save their money, don’t over install their panels, there’s little need under most circumstances to hit the 1.0-second time frame.     When working with a sound consultant, be sure to ask how long their company has been in the industry, and how long that particular person has been with the company.   Longevity in the field of sound control speaks to a long healthy track record of satisfying tens of thousands of satisfied customers, but online these days, pretty websites don’t always speak to the level of knowledge and background experience your particular sound control project will require.   Most clients have one soundproofing project to tackle, and that’s it.   So rely on the longer track records, and put your goal of 2.0 seconds or less into the hands of industry experts who have stood the test of time.

For questions related to your soundproofing treatment, and help to target your sound panel coverage for a 2.0 second reverb time, contact NetWell Noise Control at 1-800-638-9355 or visit them online at

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