@ctrl recently showed some interesting data regarding the masking effect which limits the audibility of low frequency harmonic distortion in speakers
The effect of the masking does change with frequency and fundamental amplitude. Higher distortion is required before it becomes audible with higher fundamental level. Please note the remark about the 2nd 3rd harmonic value of 10%. This appears to be a test equipment error, it would be much lower.
Also note that these are a test stimulus of a pure tone. It is easier to hear the distortion with this than with a music signal.
To investigate further I decided to perform a similar test. The following is just a start, further tests will follow.
I replicated (as far as possible) the distortion signature of a typical small speaker playing at 96dB SPL 1m. Luckily the free REW software has functionality to add harmonic distortion to signals so actually an easy thing to do and something any of you can try for yourselves.
A tone at 78Hz and 85dB /1m was played and the distortion levels for harmonics 2 to 5 were measured and set using an earthworks M23 mic.
The distortion was switched on and off several times and the FFT and sound is captured in the video below.
Its best to set the playback to HD and full screen so you can see the numbers.
So can people hear the distortion?
Try playing it back at low through to high levels. If you go up to 96db please only do it for a short time.
.
.
The effect of the masking does change with frequency and fundamental amplitude. Higher distortion is required before it becomes audible with higher fundamental level. Please note the remark about the 2nd 3rd harmonic value of 10%. This appears to be a test equipment error, it would be much lower.
Also note that these are a test stimulus of a pure tone. It is easier to hear the distortion with this than with a music signal.
To investigate further I decided to perform a similar test. The following is just a start, further tests will follow.
I replicated (as far as possible) the distortion signature of a typical small speaker playing at 96dB SPL 1m. Luckily the free REW software has functionality to add harmonic distortion to signals so actually an easy thing to do and something any of you can try for yourselves.
A tone at 78Hz and 85dB /1m was played and the distortion levels for harmonics 2 to 5 were measured and set using an earthworks M23 mic.
The distortion was switched on and off several times and the FFT and sound is captured in the video below.
Its best to set the playback to HD and full screen so you can see the numbers.
So can people hear the distortion?
Try playing it back at low through to high levels. If you go up to 96db please only do it for a short time.
.
.
Last edited: