TSOS, thank you for your post. The bright line at 700Hz was from the booster fans in my building’s A/C system, and I found a way to turn them off. I’m getting intermittent noise from the outside A/C unit for an adjacent building. I tried recording in my SUV using the Android app Smart Recorder by SmartMob v13.0, but I prefer the sound I get with the Samson Q2U mic in my office. So I’m just recording when that A/C unit isn’t running, which is mostly at night when the world gets quieter anyway.
I did try a notch filter on my breathing noises. The inhaling noise is much wider in the frequency domain than the fan noise, so applying the notch filter across the full time domain recording changed my voice too much. Instead I was looking for a gated notch filter and never found one, but I’m currently happy with gated low-pass filtering using Audacity’s Noise Gate “Gate frequencies above (kHz)”; see my discussion here.
I honestly haven’t experimented much with the Sensitivity and Frequency Smoothing (bands) settings within Noise Reduction. I just now tried 12, 12, 0 and it seemed to mess with my “ess” sounds a bit.
Applying Noise Reduction to one of my chapter files recorded with just room noise (no A/C or booster fans), NR 12,12,0 and NR 12,6,6 have almost identical ACX Check results.
NR 12,6,6
Peak level: -3.50 dB Pass
RMS level: -21.20 dB Pass
Noise floor: -82.18 dB Pass
NR 9,6,6
Peak level: -3.50 dB Pass
RMS level: -21.19 dB Pass
Noise floor: -79.23 dB Pass
NR 6,6,6
Peak level: -3.50 dB Pass
RMS level: -21.18 dB Pass
Noise floor: -76.28 dB Pass
Koz, you corrected my, “ACX has a noise floor range” to “ACX has a noise floor limit” – that is, a noise floor higher than -60dB RMS will be rejected. Also, that dead silence “biases the acceptance officer to look closely for other errors.” Is there any ACX rule-of-thumb as to what is close enough to dead silence to raise that red flag… do you think it’s -80dB? -85dB? -90dB? I ask because I really prefer the NR 12,6,6 result, while in 9,6,6 and 6,6,6 I can still hear the room noise (when using headphones). I’d rather the room noise be as low as possible while still getting ACX acceptance.
Thanks.
Zash
p.s. From this topic, it looks like a noise floor below -90dB is a problem, and perhaps the best range for ACX submission is -65dB to -80dB. Thoughts?