Here are high-resolution spectrograms for Speech.wav file (fragment from 4-th to 8-th second) after noise reduction with different commercial systems.
Features that can be observed on spectrograms:
Hover a mouse over the algorithm name to show a spectrogram, click for loading a WAV file (size is around 1 Mb). |
Original noisy recording | no processing | speech with background noise and hum |
Adobe Audition 1.5, 2.0 | reduction = 15 dB, spectral decay = 10% | some hum echoing the speech, good overall quality |
Algorithmix NoiseFree | ratio = 25 | incomplete suppression of hum, good overall quality |
Audacity | artifacts: added low-frequency hum and a click around 1.7 sec, large amount of "musical noise" artifact - local bursts of energy on a spectrogram | |
BIAS SoundSoap | incomplete suppression of hum | |
BIAS SoundSoap Pro 2 | snapshot mode | musical noise, incomplete suppression of hum, noisy echoes |
BIAS SoundSoap Pro 2 | adaptive mode | slight loss of bright timre, good overall quality |
CEDAR DNS1000 | higher threshold, max suppression | artifacts: triggering of noise gates by low-level sounds, loss of bright timbre |
iZotope RX | algo. C, reduction = 15 dB | |
iZotope RX 2 | algo. D, reduction = 15 dB | |
Magix Audio Cleaning Lab | incomplete suppression of hum | |
Sonic NoNoise 7.3 | sharpness = 2.0 | incomplete suppression of hum, loss of bright timbre |
Sonnox Restore | reduction = 15 dB | weak suppression of hum, artifacts: clicks around vocal sibilants |
Sony Oxford Denoise 1.3 | reduction = 15 dB | weak suppression of hum |
Sony (Sonic Foundry) Noise Reduction 2.0 | mode 2, reduction = 25 dB | incomplete suppression of hum |
TC Electronic BackDrop | high threshold | incomplete suppression of hum, some amount of musical noise, good overall quality |
Voxengo Redunoise 1.5 | linear phase, max suppression | weak suppression of hum |
WaveArts MR Noise 5.3 | amount = 15 dB, threshold = 6 dB | incomplete suppression of hum |
Waves X-Noise | threshold = 20, reduction = 50 | incomplete suppression of hum |
Waves W43 | manual selection of params | gating, incomplete suppression of hum |
Waves WNS | suggest, threshold = -30 dB | gating, incomplete suppression of hum |
Waves Z-Noise | threshold=12, reduction=max | sometimes noise is accompanying speech, some amount of musical noise, good overall quality |