ANSI/AMCA 320-23: Sound Testing Of Fans

Electric fan adhering to sound guidelines in ANSI/AMCA 320-23.

A slower fan speed does not produce a lower sound level. So, what determines a silent fan? The lowest fan sound level during operation is achieved at the highest fan total (mechanical) efficiency. This means the more efficient the fan, the lower the airstream turbulence and resulting fan noise. ANSI/AMCA 320-23: Laboratory Method Of Sound Testing Of Fans Using Sound Intensity establishes a method of determining a fan’s octave band sound power levels.

What Is ANSI/AMCA 320?

ANSI/AMCA 320-23 applies to fans of all types and sizes. The American National Standard specifies guidelines on suitable test environment acoustical characteristics, the measurement surface, and the number of intensity measurements. It is limited to the determination of airborne sound emission for the specified setups. The basis of its the test method originates in ANSI/ASA S12.12 but differs because it covers a wider frequency, contains requirements somewhat more specific and restrictive than those of ANSI/ASA S12.12, and provides for sound power level adjustments.

Sound power levels are determined using sound intensity measurements on a measurement surface that encloses the sound source. A measurement surface is defined as that which encloses the entire fan, fan inlet, or fan outlet, depending upon the objective of the test. The sound power level of fans should be calculated using the surface area and the measured sound intensity data.

Vibration is not measured, and the sensitivity of airborne sound emission to vibration effects is not determined.

What Is the Difference between Sound and Noise?

When air is moved, small, repetitive pressure disturbances are imparted to the air. When these pressure disturbances are sensed by a hearing mechanism (your ear), sound or noise is created.  The difference between sound and noise is that all noises are sounds while not all sounds are noises. Sounds can be used to communicate, warn and navigate, and as a form of entertainment; noise is an unwanted or unpleasant sound. Moreover, ANSI/AMCA 320-23 applies to sound as the sound pressure level, which describes the loudness level of the sound (often compared to the brightness of a light bulb), is used to measure fan noise.

How Is Fan Noise Measured?

Sound pressure level is defined asthe amplitude of pressure oscillations at some location. It is dependent on location, distance, and environment. The sound level of fans is expressed in a unit called the sound pressure level and is denoted by dB(A); it is expressed in decibels (dB) with a reference level of 20 µPa. The “(A)” indicates that sound pressure levels are “A-weighted.” This A-weighting corrects frequency measurements to replicate the frequency response of human hearing.

The sound pressure level of fans is measured by a sound level meter located 1 m from the fan’s intake side in an anechoic chamber. Since the measurement is done with the fan suspended in their air with almost no obstructions around it, the measured value is the sound pressure level when the airflow is equal to the maximum airflow.

ANSI/AMCA 320-23: Laboratory Method Of Sound Testing Of Fans Using Sound Intensity is available on the ANSI Webstore.

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