Testing to AMCA Standards
Reliable, Accurate Sound Testing
The goal of sound testing is to reduce noise during fan operation, particularly for noise-sensitive applications. By measuring and analyzing the noise generated by air impellers — and then acting on the results — Revcor helps our customers achieve their noise reduction requirements.
Our sound testing is conducted in accordance with Air Movement and Control Association (AMCA) Standard 300 Reverberant Room Methods for Sound Testing of Fans. This standard applies to fans of virtually all sizes and types, and offers a method to reliably and accurately determine the sound power levels of a fan. Standard 300 applies to the actual testing procedures, the room used during the measurement, and the reporting of the results.
In addition to establishing fan sound level ratings, Revcor is capable of troubleshooting noise issues. We follow the AMCA standard to test inlet sound power, outlet sound power and total sound power. Using a rotating incident microphone, we collect measurements from a very large set of data points, and then verify all results with redundant equipment.
About Fan Sound
Revcor understands sound. We can improve a fan’s overall sound quality through product design, improved application of the product, or recommendations for comprehensive system design improvements. Because fan sound is a key element of the product’s performance, we think it’s important that our customers learn how fan sound is generated and measured. A brief summary about fan sound follows.
Fan sound arises from various aerodynamic mechanisms occurring inside the fan as air moves through the systems and over the impeller or wheel. In addition, the operation of the fan drive, motor and bearings causes mechanical sounds. Resonant sound is created by the interaction between system components. The distinct combination of all these sounds is what our ears recognize as fan sound.
Loudness: Sound Power vs. Sound Pressure
AMCA Standard 300 is used to determine fan sound power, or the decibel level of sound produced by the fan independent of its environment. How does this differ from sound pressure? The distance of our ears from the source plus the acoustical environment combine to determine the sound pressure level.
Published sound ratings take many factors into account, including installation type, fan design and size, fan rating, and loudness/amplitude as measured by sound power and sound pressure (in decibels and sones), and frequency (in Hertz).
Sound Level Perception
At what level is the noise from a fan unacceptable? People hear sounds that are between 0 (our hearing threshold) and 140 decibels (pain threshold). Normal conversation occurs at about 60 dB, while loud noise is recorded at about 85dB and uncomfortable noise occurs at 120 dB. Determining the optimal noise level is complex because we cannot know for certain the environmental conditions in which the fan will operate or the distance between a person and the fan.
Fan sound level (independent of distance and acoustical environment) is less accurate than the sound pressure level, which takes into account the location of the listener and the sound source. While a fan manufacturer does not know exactly where their products and users will be located, they have been able to make assumptions that help them determine the expected sound pressure levels. It has been concluded that the sound pressure level is 11.5 dB lower than the sound power level, meaning that we know how the human ear will hear the loudness of the fan’s sound. Using this measure lets the OEM ensure that the fan selection is acceptable for a particular application.