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Audio SNR & Dynamic Range

Calculate audio signal-to-noise ratio, dynamic range, and equivalent noise bits from signal and noise floor levels.

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Formula

SNR = V_signal − V_noise (dB)

SNR— Signal-to-noise ratio (dB)

How It Works

Signal-to-Noise Ratio (SNR) in audio systems quantifies the ratio of the desired signal level to the background noise floor, expressed in decibels. SNR (dB) = Signal_level_dBV − Noise_floor_dBV. A higher SNR means a quieter, cleaner recording or playback chain. Dynamic range is the difference between the loudest undistorted signal and the noise floor, and for an ideal system it equals the SNR. The linear voltage SNR expresses the same ratio as a simple number: SNR_V = 10^(SNR_dB / 20). An approximate equivalent noise bits figure (ENOB) can be estimated as SNR / 6.02, since each bit of an ideal ADC contributes ~6.02 dB of SNR (from the quantisation noise formula SNR = 6.02N + 1.76 dB). Professional audio systems typically achieve −90 to −130 dBV noise floors, yielding SNRs of 90–120+ dB.

Worked Example

Signal level: 0 dBV (1 V RMS). Noise floor: −90 dBV. SNR = 0 − (−90) = 90 dB Linear voltage SNR: SNR_V = 10^(90 / 20) = 10^4.5 = 31,623 : 1 Effective noise bits: ENOB ≈ 90 / 6.02 ≈ 14.95 bits This corresponds to a high-quality 16-bit consumer audio interface. To achieve CD-quality (96 dB SNR theoretical for 16-bit), the noise floor would need to be −96 dBV. Studio 24-bit equipment typically achieves −110 to −120 dBV noise floors.

Practical Tips

  • ✓For vinyl and tape capture, a 70 dB SNR is often acceptable; for digital distribution masters, target 100+ dB. The chain is only as quiet as its noisiest link — identify and address the worst stage first.
  • ✓Use balanced (differential) interconnects for long cable runs to reject common-mode noise by 20–60 dB, dramatically improving SNR of the connected gear without changing any component.
  • ✓Recording engineers use the 'noise floor check': mute the mix, push monitor volume to maximum, and listen. Any audible hiss, hum, or noise reveals the limiting SNR of the signal chain.

Common Mistakes

  • ✗Confusing SNR with dynamic range when THD (harmonic distortion) is present — SNR measures noise only, while THD+N (total harmonic distortion plus noise) includes distortion products. In high-end equipment, THD+N can be dominated by distortion rather than noise.
  • ✗Measuring noise floor at the wrong impedance — the noise floor of an audio interface measured unloaded may be 10+ dB lower than when connected to a real source impedance. Always compare SNR specs under the same conditions.
  • ✗Stacking too many gain stages — each amplifier stage adds its own noise. A chain of three stages each with SNR = 90 dB will have a total SNR lower than any individual stage; the first (input) stage dominates and must have the lowest noise.

Frequently Asked Questions

For mixing and mastering, SNR > 100 dB is standard. For distribution (streaming, CD), 90 dB SNR (16-bit equivalent) is the minimum. Broadcast production targets 110+ dB. Consumer gear at 80–90 dB SNR is acceptable for casual listening.
dBV references 1 V RMS (0 dBV = 1 V). dBu references 0.7746 V RMS (the voltage that delivers 1 mW into 600 Ω). 0 dBu ≈ −2.2 dBV. Professional audio equipment often uses dBu for levels, while the noise floor is quoted in dBV or dBu depending on the manufacturer.
For an ideal N-bit ADC, SNR = 6.02N + 1.76 dB. A 16-bit ADC gives ~98 dB, a 20-bit ADC gives ~122 dB, and a 24-bit ADC gives ~146 dB theoretical maximum. Real-world ADCs fall short of this ideal by 10–30 dB due to thermal noise, jitter, and circuit imperfections.

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