Octave band measurements

Octave band is a term you may have come across in relation to noise measurements which can leave the non-noise-geeks scratching their heads and wondering what the hell this nonsense is and do they have to do it for a noise assessment. 

Is octave band measurement necessary for a noise assessment?

Simply put, no, you do not have to do it as part of a noise assessment. It is not a mandatory part of a noise assessment and your noise assessment can be perfectly valid and do its job without it.

However, if your meter can do octave band measurements then I would advise that you do as it can make your results much more accurate and be extremely useful when it comes to assessing how effective hearing protection is. So, you don't have to do it, but if you are buying a noise meter I would recommend you get one which can do it.

What use are octave band measurements?

Their main use in a noise assessment comes when you are at the stage of trying to decide if current hearing protection is adequate for the noise risk, or if you are wanting to specify new styles of hearing protection for the site.

Hearing protectors like plugs and muffs have a figure which they are said to reduce the noise levels by, for example 27dB, called the SNR. But, hearing protection does not offer that level of protection at all frequencies and it will perform better at some than others. So you may get say 27dB of protection at the high pitched frequencies, but maybe only 15dB of protection at the lower frequencies. This is all well and good if your noise is also high pitched, but if the noise is loudest at the lower frequencies then this is where the hearing protector is not so good and the people wearing it will be exposed to more noise, and it may be so much that they are still at risk of hearing loss. 

What an octave band measurement does is measure the noise at several different frequencies, grouping them into say ten bands, and giving you a noise level for each of them. That can then be used to confirm the hearing protection is performing well not just overall, but also is good enough at the specific frequencies generated by that noise.

And there is more octave band goodness...

One big benefit of octave band measurements is that a lot of the software that comes with the better noise meters includes a database of many hearing protectors and how well they perform at the various frequencies. This means that assessing if a hearing protector is good enough is often simply a matter of hitting a button in the software and there you go, all done and a report is generated. You can also often do a report of many many hearing protectors all at once, with each showing how they would perform for that specific octave band measurement giving you a nice long list of suitable or approved hearing protectors to choose from with no manual calculations needed at all. That can be very useful and save a lot of time. And saving time and being easy is always good! 

What if you can't do octave band measurements?

If your noise meter doesn't do octave band measurements there are still ways of measuring how good hearing protectors are and all the info you can possibly need on that is on its own page on this site - SNR or HML. These are slightly less accurate but still good enough, and it can be harder to do reports on many types of protector all at once, but it is still OK, hence octave band measurement is not mandatory.