When you think of an anechoic or semi-anechoic chamber, you may picture a perfectly silent space lined with acoustic wedges.
But in reality, even the quietest test environments are not immune to a hidden adversary\u2014background noise.<\/p>\n\n\n\n
This “background noise” can stem from HVAC systems, equipment vibration, or sound leakage through cable ports.
Once it contaminates the measurement environment, it can compromise data accuracy and undermine confidence in the results.<\/p>\n\n\n\n
IInternational standards such as ISO 3744:2010 and ISO 3745:2012, which govern sound power level (PWL) measurements, define the following rule:<\/p>\n\n\n\n
The background noise level should be at least 10 dB lower than the measured sound from the Device Under Test (DUT).<\/p>\n\n\n\n
For example, if the DUT emits 40 dB at a given frequency, the background noise must be below 30 dB in that band.
This ensures the K\u2081 correction factor remains small and measurement reliability is maintained.<\/p>\n\n\n\n
Let\u2019s look at the typical formula used in sound power measurement:<\/p>\n\n\n\n
Lw = (Lp \u2013 K\u2081 \u2013 K\u2082) + 10 log(S\/S\u2080)
K\u2081: Correction factor for background noise
K\u2082: Correction for environmental influences (reflections, etc.)<\/p>\n<\/div>\n<\/div>\n\n\n\n
If K\u2081 is too large or unstable, the calculated sound power level (Lw) becomes unreliable\u2014especially critical for low-output devices such as sensors, motors, and cameras in the 30\u201340 dB range.<\/p>\n\n\n\n
To reduce background noise, the following countermeasures should be considered:<\/p>\n\n\n\n
At Sonora Technology, our solution is the proprietary BFW (Broadband Fractal Wedge) system.
This design enables chamber background noise levels below 25 dB(A), providing the ideal environment for high-precision measurements using HBK instrumentation.<\/p>\n\n\n\n
As the target sound levels of products continue to decrease, the testing environment must become quieter to keep pace.
HBK’s LAN-XI system and Type 4204 reference sound source are engineered to deliver peak performance only when background noise is sufficiently suppressed.<\/p>\n\n\n\n
With Sonora\u2019s anechoic chambers designed to meet the \u201310 dB requirement, we support stable K\u2081 correction and deliver measurement environments that ensure data integrity and promote low-noise product development.<\/p>\n\n\n\n
The quietness of an anechoic chamber is not a luxury\u2014
It\u2019s a critical infrastructure for precision acoustics, forming the foundation for valid design decisions.<\/p>\n\n\n\n
\u201310 dB below the measurement sound level.
That\u2019s the baseline for trust in your data.<\/p>\n\n\n\n
He who controls background noise controls the accuracy of testing.<\/p>\n\n\n\n
Experience the next generation of quiet development environments with the Sonora \u00d7 HBK total solution.<\/p>\n\n\n\n
For consultations on chamber design or acoustic measurement systems, please reach out to:<\/p>\n\n\n\n
Moritani Corporation, Tokyo Headquarters \u2013 Machinery Division 2<\/p>\n\n\n\n