Frank, Rick, I found my ".wav" files doing similar to what AB7E does. Except that his has MP3 raspy artifacts all over the place and mine doesn't.
Take a listen to his and mine AB7E MP3: http://www.ab7e.com/weak_signal/0_1_2_3_4_5_6_db.mp3 N3QE WAV: Sum of morse + noise: http://n3qe.org/sum.wav Just in case you are interested, the raw noise and raw morse WAV files before mixing below: N3QE WAV: My raw noise (no morse): http://n3qe.org/noise.wav N3QE WAV: My raw morse (no noise): http://n3qe.org/morse.wav Tim N3QE On Wed, Aug 21, 2019 at 3:34 PM Tim Shoppa <tsho...@gmail.com> wrote: > Will do, Frank! > > Here's an interesting exercise: > https://www.npr.org/sections/therecord/2015/06/02/411473508/how-well-can-you-hear-audio-quality > > I just ran through it and picked the uncompressed .WAV all 6 times :-) > > One giveaway to my ears is things that were clear sharp impulses in the > originals, get muddy in compression. For example the glocks at the end of > the Neil Young sample is the easiest way to tell with that one. > > Other times, it's the lack of artifacts that helped me pick the original > .WAV. For example the Suzanne Vega samples. > > Interestingly the Suzanne Vega clip was used by developers of MP3! > > On Wed, Aug 21, 2019 at 3:15 PM <donov...@starpower.net> wrote: > >> Hi Tim, >> >> As you're well aware, perfect is often the enemy of good enough. >> >> Please publish your files and let us all experience how much better they >> are. >> >> Thanks >> >> 73 >> Frank >> W3LPL >> >> ------------------------------ >> *From: *"Tim Shoppa" <tsho...@gmail.com> >> *To: *"Richard (Rick) Karlquist" <rich...@karlquist.com> >> *Cc: *"Frank Donovan" <donov...@starpower.net> >> *Sent: *Wednesday, August 21, 2019 6:30:20 PM >> *Subject: *Re: Topband: Impressive demonstration of one dB of signal >> strength improvement >> >> Rick, I agree, MP3 just muddies the sound of those examples. I regularly >> save my radio audio as 8kHz WAV and am happy with that. But I can tell if I >> convert it to MP3 that it is "off" and "wrong". The MP3 format's >> psychoacoustic encoding muddies the beginning and end of each dit AND does >> a horrible job when presented with lightning or impulse noise. >> >> Last time Frank and I talked about these examples, I made a completely >> independent set for my own use that was never compressed along the way. >> (.WAV uncompressed format). Will dig up at home. >> >> Tim N3QE >> >> >> >> >> On Wed, Aug 21, 2019 at 12:54 PM Richard (Rick) Karlquist < >> rich...@karlquist.com> wrote: >> >>> On 8/21/2019 8:16 AM, donov...@starpower.net wrote: >>> > These recordings are an impressive demonstration of the benefit of >>> > one dB of signal strength improvement in a weak signal situation. >>> > >>> > >>> > Click on the links on this website: >>> > >>> > >>> > >>> > www.ab7e.com/weak_signal/mdd.html >>> > >>> > >>> > 73 >>> > Frank >>> > W3LPL >>> >>> It seems to me that converting the files to .mp3 >>> muddies the water. Dave comments that 32 kHz >>> is "decent fidelity". It certainly isn't (IMHO) >>> decent fidelity for music. I don't know about >>> noisy CW. The .mp3 format was optimized >>> for music or possibly high S/N voice, but not CW >>> buried in noise. The operational principle of >>> mp3 (or any lossy compression) is "noise gating". >>> For all I know, the abrupt change at low S/N may >>> be an artifact of the compression. >>> >>> I don't understand the comment about "all audio files >>> were converted to .mp3 format and mixed ..." AFAIK, >>> mixing should be done before any compression. >>> >>> Using "band noise" also muddies the water. It would >>> have been better to use the proverbial Additive >>> White Gaussian Noise (AWGN), to get reproducible results. >>> Dave comments that "spikey" noise is another hard to >>> quantify condition. I have noticed anecdotally that >>> 160 meters tends to have spikey noise vs AWGN on say >>> 20 meters. This results in clearly audible signals that >>> can't be copied by ear on 160 meters, whereas on 20 >>> meters, I seem to be able to get solid copy on signals >>> that are just barely detectable. This is a poorly understood >>> phenomenon. >>> >>> Another issue with reproducibility is the audio bandwidth. >>> The brain tends to be able to provide some audio filtering >>> of its own. IOW, I believe that you will find that >>> a 250 Hz bandwidth will give less than a 3 dB advantage >>> vs 500 Hz for the threshold of copy. At narrow bandwidths, >>> ringing becomes an issue. Typical brick wall filters in SDR's >>> may or may not be optimum for copying a CW in noise >>> (and in the absence of QRM). My Flex 6700 uses a >>> gazillion poles "because they can" :-) >>> >>> Rick N6RK >>> _________________ >>> Searchable Archives: http://www.contesting.com/_topband - Topband >>> Reflector >>> >> >> _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
