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Audio / Acoustics High-Fidelity Testing

Precision THD+N, crosstalk, and bandwidth assurance

Overview

High-fidelity audio validation ensures linearity, channel separation, and consistent bandwidth. We combine THD+N/SINAD/IMD sweeps with channel-coherency checks to locate distortions and imbalance.

Industry Challenges

1

THD+N and SINAD out of spec

2

Crosstalk between channels

3

Inconsistent filter bandwidth and phase response

4

Noise floor buried in switching artifacts

5

Mismatch between analog/digital stages

Standards & Specifications

StandardDescriptionNotes
AES17-2015AES standard method for digital audio equipmentDefines THD+N, channel separation, frequency response measurements for digital audio (§3.5 THD+N, §3.7 Crosstalk)
IEC 61606-1:2009Digital audio parts - Basic measurement methodsAudio characteristics measurement including SINAD definition (§3.1.10)
IEC 60268-3:2018Sound system equipment - Part 3: AmplifiersAmplifier measurement methods including IMD (SMPTE/CCIF/DIN methods)
IEC 60268-5:2003Sound system equipment - Part 5: LoudspeakersLoudspeaker measurement methods and parameters
IEC 61672-1:2013Electroacoustics - Sound level metersSound level meter specifications and accuracy requirements
ITU-R BS.468-4Audio-frequency noise measurementNoise voltage measurement with quasi-peak weighting
ITU-R BS.1770-4Loudness measurement algorithmsProgramme loudness and true-peak level measurement

Core Principles

THD+N / SINAD

THD+N (%) = √(ΣV²_harmonics + V²_noise) / V_fundamental × 100% SINAD (dB) = 20·log₁₀(V_signal / V_noise+distortion) = -20·log₁₀(THD+N) Measure at multiple levels and frequencies to capture nonlinearity. Ref: AES17-2015 §3.5, IEC 61606-1:2009 §3.1.10

Intermodulation Distortion (IMD)

Two-tone test shows sum/difference tone distortion: IMD (%) = √(V²_f1±f2 + V²_2f1-f2 + ...) / V_fundamental × 100% Common methods: SMPTE (60Hz+7kHz, 4:1) or CCIF (19kHz+20kHz, 1:1) Ref: IEC 60268-3:2018

Crosstalk / Channel Separation

Crosstalk (dB) = 20·log₁₀(V_leakage / V_driven) Low crosstalk (<-80 dB) ensures proper channel isolation for stereo/multichannel systems. Ref: AES17-2015 §3.7

Bandwidth & Phase

Frequency response plotted via swept sine; group delay quantifies dispersion. Bandwidth extends until response drops -3 dB.

Noise Floor

Use low-noise source and FFT to map noise spectral density: PSD (dBV/Hz) informs audible noise limits.

Typical Test Tasks

Distortion & Noise

  • THD+N SweepMeasure across 20 Hz–20 kHz at reference levels
  • SINADConfirm signal-to-total-noise ratio
  • IMD (SMPTE/CCIF)Two-tone distortion evaluation
  • Noise FloorFFT with low-noise source for hiss/rumble

Channel & Phase

  • CrosstalkDrive one channel, measure adjacent leak
  • Gain MatchingCompare amplitude across channels
  • Phase CoherenceBinaural phase and polarity checks
  • Group DelayMeasure dispersion through filters

Bandwidth & Response

  • Swept SineFrequency response for loudspeakers or filters
  • Step ResponseTransient behavior reveals overshoot
  • Filter Roll-OffCheck -3/-6 dB slopes and linearity
  • Digital Audio ChainVerify ADC/DAC linearity and jitter

System Coherence

  • Impedance CurveSpeaker/driver impedance vs frequency
  • Acoustic CouplingMicrophone or speaker placement influence
  • LatencyVerify real-time responsiveness in DSP chains
  • Report TemplatesAutomated pass/fail reporting for QC

Recommended Configuration

Audio Analyzer

  • THD+N/SINAD/IMD capability
  • Two-tone generator option
  • Auxiliary channel for crosstalk
View Audio Analyzers →

Low-Noise Signal Source

  • Low distortion, low noise
  • Sweep and multi-tone support
  • Phase reference for vector measurements
View Signal Generators →

Mixed-Signal Oscilloscope

  • High vertical resolution
  • FFT and spectrum views
  • Digital audio decode (optional)
View Oscilloscopes →

Accessories

  • Balanced/unbalanced audio cables
  • Audio fixtures and load boxes
  • Calibrated microphones or speaker cans
  • Acoustic isolation enclosures

Software

  • Audio distortion analysis suites
  • FFT/noise floor mapping tools
  • Automated A/B comparison scripts

Our Services

Audio Test Plan

Define THD+N, IMD, and bandwidth protocols

Channel Matching Review

Validate stereo or multichannel gain/phase balance

Acoustic Setup

Microphone placement, room treatment, and isolation

Automation & Reports

Batch testing with pass/fail reports for QA

Audio engineers familiar with AES/IEC standardsMulti-brand support: Keysight / R&S / TektronixRental and pre-owned options available

Our Capabilities

Distortion Testing

THD+N, SINAD, and IMD measurements with tone sweeps

Channel Consistency

Crosstalk, gain, and phase matching across stereo/multi-channel paths

Noise Floor Verification

Low-noise sources and spectral analysis for noise budgeting

Bandwidth & Filter Checks

Frequency response, group delay, and filter roll-off verification

Recommended Products

Audio

Audio Analyzers

Precision THD+N and SINAD source/measure

View Products →
Low-Noise

Low-Noise Signal Sources

Distortion-free sine sweeps up to audio band

View Products →
High-Resolution

High-Resolution DMMs

Support for AUX input and low-frequency noise

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Mixed-Signal

Mixed-Signal Oscilloscopes

Time-domain harmonic insight and jitter analysis

View Products →

Key Applications

✓Hi-Fi amplifier validation
✓Pro audio and broadcast equipment QA
✓Headphone/earbud and speaker R&D
✓Automotive infotainment audio
✓Acoustic sensor and mic testing

Need high-fidelity audio testing?

Tell us your distortion, noise, and bandwidth targets so we can recommend a complete test stack.

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