Microstar Laboratories, a maker of data acquisition processor (DAP) systems for PC-based measurement applications, has released a software package for audio analysis for use with its xDAP systems.
Using the package with two extra lines of configuration script is said to add high-precision 1.3 octave analysis to measurement applications.
In effect, the user's general-purpose xDAP system is transformed into a specialised audio analyser instrument.
The package is available for free download from the company's website.
It includes a technical note explaining how to customise the software to optimise individual applications.
Users can send the octave analysis results to the PC application environment of their choice.
A 1/3 octave analysis partitions a power spectrum into logarithmically-spaced frequency bands, corresponding to the manner that audio tones are perceived.
There are alternative solutions for doing this, with various trade-offs in capability and price.
Single-purpose dedicated instruments do an excellent analysis, but building a good instrument is challenging and costs are high.
GUI-based analytical software systems offer signal processing toolkits that can perform a similar analysis, but this too is expensive and ties the application to a high-overhead software environment.
The solution of using an xDAP system and this free configuration software results in a streamlined system with high-performance, low net-cost, and compatibility with any software environment.
The embedded 1/3 octave analysis uses the MIXRFFT processing command - part of the DAPL 3000 operating system - for its frequency analysis.
Processing the full audio range, ANSI band 10 (from 8.7Hz) to ANSI band 44 (to 22.7kHz), requires large data sets.
The MIXRFFT command supports this processing, with high precision.
The THIRDOCT analysis then does the 'bookkeeping' to identify and summarise the logarithmically-spaced 1/3 octave bands.
The technical note explains how to co-ordinate the data capture, classic frequency analysis, and 1/3 octave analysis activities.
The resolution of the 1/3 octave analysis is said to be extremely high.
This differs from behaviours that users would get from typical 'reference implementation' instruments using sixth-order bandpass filters (or their digital equivalents).
This means that a signal registering as a crisp single band in the high-precision analysis would appear as a 'multi-band smear' in a traditional instrument.
If it is necessary to match such traditional behaviours, supplemental processing to distribute the high-resolution spectrum results into neighbouring bands is possible.
Other supplemental processing could convert the results to RMS amplitude, dB gain, or physical power units.
