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Tonality ISO 1996-2:2017    1/3,1/3LF

Strutt|Environmental Noise|ISO 1996-2:2017 Tonality tests for the presence of tones by comparing the time-averaged sound pressure level (SPL) in a given 1/3 octave band with the time-averaged SPLs in the adjacent two 1/3 octave bands.

For a tone to be identified as present, the time-average SPL in the band of interest must exceed the time-averaged SPLs of both adjacent 1/3 octave bands by some constant level difference.

The assessment is carried out in accordance with Annex K of ISO-1996-2:2017. This Annex is provided for informative purposes only - it is a suggested methodology for identifying tones.

The aforementioned constant level differences given in Annex K are described as "possible choices"; nevertheless, these are the values that we have chosen to implement in Strutt. They are:

• 15 dB in low-frequency bands (25 Hz - 250 Hz)
• 8 dB in mid-frequency bands (160 Hz - 400 Hz)
• 5 dB in high-frequency bands (500 Hz - 10,000 Hz)

References:

• ISO 1996-2:2017 Annex K Acoustics -- Description, measurement and assessment of environmental noise -- Part 2: Determination of sound pressure levels