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Sound and Vibration Basics

Tone and Tonal Assessment


Tonal noise typically contains a noticeable - or discrete - continuous note which can include hums, hisses, screeches or droning sounds; these particular noises are difficult to prove and can quite often be disputed

Example of tone assessment screen

Created for use with Bruel & Kjaer's 2250 sound level meter, this tone assessment application provides simultaneous measurements of the LAeq - as well as other broadband parameters. It provides on-the-spot calculations for tone-corrected rating levels and the results are displayed in accordance with ISO 1996-2 Annex C.

Using ISO 1996-2, provides an objective method for verifying the presence of tones, the tone assessment option produces instant, objective feedback allowing users to determine whether they have identified the problem or need to make further measurements.

The type 2250 instruments are also equipped with a tone generator so that an audible tone can be compared with the measured sound.

The tone assessment software is available as an add-on with B&K's FFT Analysis module for the Type 2250 sound level meter. The 2250 meter is very user-friendly with a large dynamic range and frequency resolution allowing the operator to simply position the analyser in an appropriate location and start measuring.

Objective measurements can be very comprehensive in detail, so it's helpful to have a sound recording of the noise for the benefit of a non-technical audience. The Bruel & Kjaer Tone Assessment tool is also compatible with the sound recording option included with all 2250 meters available for hire from Gracey & Associates.

The above extract is courtesy of Bruel & Kjaer - see also the B&K 2250 FFT and Tone Assessment Meter