You would only hear the 1 kHz tone during immunity testing. It's very
unlikely that one would hear anything noticeable when the product is in
normal use. Electret microphones almost always have capacitors included
to give immunity at cellphone frequencies, for obvious reasons, and
their small dimensions and shielding confer immunity at lower
frequencies. Passive headphones are most unlikely to demodulate RF
signals. Active headphones, (wireless, noise-cancelling) are rarely
supplied as accessories with a product, so the product manufacturer need
not take them into account.
It's easy to tell if the 1 kHz is coming from the product; just measure
the output voltage at the headphone socket with a well-screened audio
voltmeter, with and without the microphone muted.
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK
On 2018-09-05 07:00, Amund Westin wrote:
Wired headsets and microphones connected to a product, often acts as
receiver for induced RF fields. That means you quite often hear the
1kHz modulation tone under the RF immunity tests. This is quite
annoying for the user and above a certain level, not acceptable.
To avoid such phenomena is quite a big task to conduct. But have
anyone of you any experience how to determine if the headsets /
microphones or the connected final product is the source to this
problem? 3rd. party headsets / microphones have of course different RF
immunity performance, and after a lot of testing, you might be able to
find headsets / microphones that are does not pick up fields and the
hearing audio noise level is acceptable.
I assume that the final product may have great level of immunity, but
as long the headsets / microphones has poor immunity level, you will
have this audio problem anyway.
Has anyone been into this problem before?
BR
Amund
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