EPR-000014 Datasheet, PDF (16/28 Pages) Power Integrations, Inc. – Engineering Prototype Report - 3 W Universal Input TinySwitch-II TNY264 Power Supply

EPR-000014 – 9 V, 0.33 A, 3 W TNY264 Adapter
22-Feb-2002
8.7 Acoustic Emissions
The power supply was subjected to acoustic emissions measurement. The worst-case
noise was measured for variations of both AC line and output loading conditions. These
results are presented in Figure 12 and Figure 13. In all cases, acoustic emissions were
below acceptable levels.
The test unit was placed in an anechoic acoustic chamber, with a microphone located
approximately 1” (25 mm) above the transformer (T1) as shown in Figure 11. The power
supply was oriented in a horizontal position with the power supply output loaded via an
external Kikusui electronic load. The microphone output was fed to an Audio Precision
audio analyser to provide the measurements shown.
Microphone
Figure 11. Test Arrangement for Audio Noise Measurement
The curves shown indicate the spectral content of the noise generated by the supply
once the ANSI-A weighting factor has been applied.
The audio limit line (Figure 12, 13) visible at +35 dB represents the generally accepted
threshold for power supply audio noise. A discrete audio frequency amplitude was used
rather than a dBA value (dBA represents the whole audio spectrum). Large peaks may
not raise the dBA value yet can result in unacceptable perceived noise.
As a reference, the approximate dBA background noise floor level is 30 dBA. The
microphone sensitivity is such that 20 µP = 0 dB SPL.
Power Integrations, Inc.
Tel: [phone] Fax: [phone]
www.powerint.com
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