Bill W4ZV wrote:
>
>
>
> David Woolley (E.L) wrote:
>>
>> The main source of published research on real time noise reduction of
>> audible signals seems to be the hearing aid industry. I just came
>> across this article suggesting that hearing aid noise reduction
>> strategies make people think that the noise is less sever, but don't
>> actually make the signal any more intelligible.
>>
>> Trends in Amplification, Volume 10, No. 2, June 2006: Acceptance of
>> Background Noise, Mueller et al.
>> <http://tia.sagepub.com/cgi/reprint/10/2/83.pdf>
>>
>
> That's an interesting article David! It agrees with my feelings over the
> many years I've tried various types of noise reduction. Sometimes I think
> we're fooled by the level changes introduced by NR, when in fact we could
> probably do as well simply by turning AF Gain down a little.
>
> A few years ago when NQ5T and I both had Orions, I challenged Grant to
> measure the actual S/N with NR on and off. At narrow bandwidths, there
> was no difference in measured S/N. Of course this was for CW where NR
> simply builds a narrow filter around a discrete signal.
>
This was for Orion II, but for anyone interested, here's the summary by
Grant NQ5T:
http://lists.contesting.com/archives//html/TenTec/2006-03/msg01118.html
On March 25, 2006, NQ5T wrote:
[TenTec] Orion II NR Performance Measurements
I won't bore you with the setup here, but will be happy to provide details
to anyone who is interested. Consistent results were obtained by two
independent methods: (1) graphical computation of SNNR, and (2) spectral
analysis software that directly computes an estimate of SNR.
The results are as follows (LCW, 1000Hz spot tone, NR=9)
BW=3000Hz: SNNR improves by approx 1dB with NR=9.
BW=500Hz: SNNR degrades by approx 2dB with NR=9.
There is improvement at 3 Khz bandwidth, but it's negligible. At 500 Hz
(and anything below that as well) you're better off without NR at all. The
distortion created by NR at any bandwidth in both CW tone and SSB voice is
very unpleasant compared to typical noise reduction products.
Even without having a v1 Orion to compare with I'm basically moving from the
"uncertain" bench to the "put it back the way it was" bench.
Grant/NQ5T
--
View this message in context: http://n2.nabble.com/K3-NR-tp3515659p3542357.html
Sent from the [K3] mailing list archive at Nabble.com.
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