In an attempt to quantify this, I installed OSHA's free NIOSH app, which
measures noise, onto my iPhone 7 and tried it out. It's not a
measurement instrument, mind you, so the absolute numbers are highly
questionable. But the relative numbers are interesting. I held the
phone at eye level between me and my computer monitor, about 2 feet from
the amplifiers. Here are the results:
dB measured with NIOSH app, rounded to two significant digits:
46 - for comparison - an Alpha 89 running as normal
48 - KPA1500 at fan level 0 (i.e. PS fans only)
51 - fan level 1 (i.e. center fan plus PS fans)
57 - fan level 2 (all fans on)
64 - fan level 3 (all fans on)
67 - fan level 4 (all fans on)
76 - fan level 5 (all fans on)
Similar to other comments I've read, I find up through level 2 to be
okay. At 3 and above I need headphones or, better still, noise
cancelling ones. My experience thus far is that on SSB in normal
conversation at 1500W it stays at level 0 with an occasional excursion
into level 1 if I'm long winded. In the CW WPX test last weekend,
strictly in S&P mode, it stayed at level 0. Experiments with CQing and
on FT-8 are yet to come and I'm sure will require higher speeds.
73,
Chris, W2PA
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