

by W.A. Steer PhD

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Audio Spectrum Analyser

This page describes a free audio spectrum analyser which you can download. It uses fast Fourier transform (FFT) to give a real-time ('live') spectrum display on your screen.

Applications

Understanding audio quality and the effects of digital compression (e.g. MP3) on audio bandwidth

Detecting problems in audio recording

Identifying problems with audio processing, e.g. in laptop beamforming-microphone algorithms/drivers

Teaching and training

Speech and audio research

General scientific applications

Acoustic noise analysis and R&D into making quieter appliances

Radio amateurs

Feature and Specifications

Runs under Microsoft Windows 95, Windows XP, Windows Vista, Windows 7 and newer.

Samples an audio stream in 16-bit stereo, then uses a Fast Fourier Transform to yield the spectral analysis in real time.

Bargraph peak-level indicator shows time-domain peak levels and onset of clipping distortion (spectrum also goes red).

Stereo input, dual bargraph, choice of Left, Right, sum or difference for frequency analysis

User selection of sampling-rates, including 32kHz, 44.1kHz, 48kHz

Supports multiple 'wave input' devices (multiple soundcards, and/or the newer Windows Vista/7 sound model).

Spectrum obtained using FFT with Hanning (raised-cosine) window-function.

User-selection of different FFT transform sizes to trade-off time response and spectral resolution. New in v3.7

Choice of linear and logarithmic (dB) vertical scales (including 'perceptual' A-weighted scales)

Implemented correct 'A'-weighted displays (rather than Fletcher-Munson/Terhardt). Now optional for all visualisations.

Vertical scale calibrated as fraction of digital full scale ('FS') with currently-set mixer-settings etc.

Choice of horizontal (frequency) scales, including a logarithmic 'perceptual' scale.

Spectrograph (waterfall) visualisation options (experimental/beta feature).

Time-averaged spectral displays. New in v3.8

Self-test / demo mode, showing spectral purity and effects of windowing. New in v3.86

Option to use a couple of alternative FFT window-functions

Ability to export some spectral data to clipboard (additional improvements/disambiguations in v. 3.97)

Third-octave band analysis (v3.97)

Mel-band analysis (v3.97 - non-overlapping frequency bands)

In older versions the perceptual "A-weighted" is not actually A-weighted, but is modified by the hearing threshold according to Terhardt - see http://www.diracdelta.co.uk/science/source/t/h/threshold%20of%20hearing/source.html. Versions 3.8 onwards use actual A-weighting.

Features not yet implemented, but under consideration (roughly in order of likely implementation)

Improvements to export/save spectral data functionality

Improve axis displays in general, and add proper time axis/scales to spectrogram visualisations

Labelling/readout of precise frequency (and amplitude/energy) of prominent spectral peaks

Ability to open, play, and analyse directly from uncompressed .WAV files

Option to calibrate vertical scale, e.g. to 94dB 1kHz reference source (maybe in a future Pro/paid version)

Tidy up the stereo vector analyser visualisation

'Oscilloscope' visualisation

Tweaks for better window layout/rendering under Windows 10

Option to pause display and step back/forward though the past few seconds (and maybe a peak-hold function)

Use lookup tables to improve program efficiency for any displays using log calculations!

Grid-line option on the spectral display

Horizontal scroll option to allow close-up inspection of a narrow part of the spectrum.

...

Download

Download: SpecAn_3v97c.exe (564kB) latest version 3.97c - 16 July 2016.

New in this version: improvements to ability to export numerical data (time-average FFT) to clipboard, new third-octave band analysis, Mel-band analysis, and other minor tweaks.

Older/archive versions

Download: SpecAn_3v93.exe (553kB) previous version 3.93 - 29 April 2016.

Download: SpecAn_3v91.exe (550kB) older version 3.91 - 29 August 2015.

Download: SpecAn_3v5.exe (532kB) much older version 3.5 - August 2013.



By downloading any of these files, you consent to the standard disclaimer.

This applet doesn't require any installation, won't touch your Windows Registry, and won't install any DLLs. Just download the .EXE and run it. There's no bundled adware or unwanted toolbars. It'll even run straight off a USB memory stick if you want.

Created: May 2011

Last modified: 1 Aug 2016

Source: http://www.techmind.org/audio/specanaly.html