Comparison of Noise Reduction Systems

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:
  • Horizontal lines at lows and mids: electric hum (part of the noise)
  • Background speckle at all frequencies: broadband noise
  • Wavy lines: voice harmonics
  • Vertical light areas at mids and highs: speech sibilants
  • Noisy cloud around 2 sec: breath
  • Vertical lines around 1.7 sec: breaking saliva during mouth opening



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