SpeakerMeasure is a free software tool from Eclipse Audio that automates the AES75 test procedure used to determine maximum SPL. SpeakerMeasure says it speeds up the measurement process and results in both repeatable and objective measurements. The Audio Engineering Society standard, released in 2022, details a test procedure for measuring maximum linear sound levels of a loudspeaker system or driver using a test signal called ‘Music Noise’ (initially M- Noise). The AES75 procedure covers two basic steps: a ‘Linear Response Check and a ‘Level Increase Test.’

In the latter, the playback level of the Music Noise stimulus is increased until specific stop conditions occur, either an unacceptable change in the transfer function’s magnitude or an unacceptable change in the coherence of the transfer function. Both stop conditions are very difficult to objectively judge by eye when watching a real-time measurement system, especially since multiple visual comparisons of the same measurement are required. By automating the data analysis and comparison with stop conditions – all continuously in real-time — SpeakerMeasure can be used by anyone with a computer and appropriate measurement equipment, including a high-quality audio interface, measurement microphones, an accurate RMS voltmeter and a reasonably high-voltage rail amplifier. (An amplifier is only needed for passive loudspeaker measurements.)