If there is the possibility of tonal noise (a very common cause of complaints), any environmental noise investigation or report (e.g. BS4142) that does not include narrow-band frequency analyses is, by definition, not fit for purpose. Consequently (confirmed by surveys) around 90% of consultant noise reports are inadequate. The key reasons are:-
Given these benefits and the fact that there are dozens of perfectly adequate and free frequency analyser apps available for smartphones, why is narrow-band analysis absent from most BS4142 noise reports?
In addition, this form of analysis massively reduces the resources spent on complaint investigation and cuts the time taken to resolve those complaints from months or years down to a few days or weeks.
The following is a simple, practical guide to the use of tonal noise analysis.
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Simply email us your recording(s) and we will carry out the frequency analysis for you. These can be in any audio format or even short smartphone video clips from which we extract the audio.
Anyone can diagnose the cause(s) of complaint-causing tonal noise, quickly, simply and at no cost.
We have the expertise to use sophisticated analysis and noise signature fingerprinting not only to identify the culprit plant, but also the precise cause of the tonal noise - e.g. out-of-balance, fan blade pass, compressor tones, gearbox gear mesh, worn bearing, blower or pump harmonic, vibratory sieves or feeders, gen-sets, acoustic or structural resonance, burner or combustion noise etc. You can benefit from this expertise by using our email analysis and diagnostic service to get both the diagnosis and the costed noise control options.
However, there is just a handful of common tonal noise sources that anyone (even noise consulants) can identify from the frequency signatures.
Important note: mains hum and gen-set tones are all at exact multiples of 50Hz and 25Hz as they are locked to mains frequency, whereas fixed speed synchronous motors run at slightly lower frequencies. This is a useful diagnostic tool as, provided you use a frequency resolution of < 0.5Hz, a 50Hz tone is electrical whereas a 49Hz tone is mechanical (a motor).
Noise complaints caused a large industrial site. We requested an off-site smartphone recording plus recordings close to suspect items of plant by email.
This whole process is a simple, fast and effective way for anyone to determine the precise cause of complaints. You can then either search our online case studies for potential best practice solutions or you can send the data to us so we can then add the costed noise control options.
EHO threatened abatement notice due to noise complaints - the company had bought ineffective noise control (enclosure and silencer). We requested recordings near the fans and in the complainant bedroom.
If this analysis had been carried out by the consultant to identify the cause of the complaints, the company would not have wasted money, EHO time and resources and the complaint would not have had to suffer unnecessarily for months.
Complex noise complaints, potentially due to multiple sources.
The complaints had dragged on for many months without identification of the causes and hence no resolution. All the contributory sources were quickly identified using frequency signature analysis and hence the optimum (and very precise) mitigation could be designed.
Tonal noise complaints had been attributed by the Environment Agency to noise from just one site due to the use of 1/3 octave analysis only. In fact, the problems were actually caused by 2 tones close together from 2 different sites. This initial misdiagnosis led to very long delays in mitigation and a huge waste of time and resources.
Not using narrow-band frequency analysis as the basis for the investigation of this tonal noise complaint proved to be very costly. The Environment Agency spent considerable time and resources with multiple site visits and noise measurements. The company also invested time and resources in its attempts to track down and mitigate the problem.
When consulted, analysis of the recordings we requested quickly showed that half the noise problem was a 75Hz gen-set tone (solved by fitting a tuned silencer) and the other half to be a 71Hz chiller fan blade pass hum from an adjacent site.