1/9/2023 0 Comments Octave bandVery easy: there are instruments, call Sound Analyzers (see one of them in Figure 2) that do that for you. But how do I go about measuring the sound level of those bands?Ī. You can see an illustration of the octave bands of a noise in Figure 1.įigure 1. It is easy to see that the width of each band increases with each band, but we won’t get into those details. (As a matter of fact you can go up or down the spectrum always dividing or multiplying the central frequency by 2, but for noise control purposes, only those are the 7 bands of interest). They are centered at the following frequencies: 125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz, and 8 kHz. So, we divide the entire spectrum of the noise in frequency bands (using filters) in such a way, that each band is one octave higher than the previous one. (It will be quite complicated and with no real advantage of listing all 20,000 frequencies!). But we are not interested in knowing all of them. Now, here is the story: sometimes (and noise control is one of those) we want to know the frequencies and the amplitudes of the components of a noise. The same applies to one of 2 kHz and one of 1 kHz.įinally, and here goes your knowledge of music, do you remember that there are 7 notes in the musical scale and the next one after the seventh sound twice as high as the first and is called “one octave higher?” If you know all of the above, you won’t have any problems with understanding the octave bands issue. In such a way a sound of 200 Hz sounds twice as high as one of 100 Hz. Another piece of information that is not strange to you is that if a tone sounds twice as high as another, its frequency is double of the first one. Also, you know that audible noise goes in general between 20 Hz and 20 kHz. You do remember that a pure tone is characterized by amplitude and frequency, right? And that noise in general is comprised by a variety of tones with different frequencies and amplitudes. Definitely not! However, this word has more than one meaning and in acoustics we do have one. Obviously that is not what you mean, right?Ī. I know that a band is a group of people who perform instrumental or vocal music. Now, you really got me! Never heard of those bands. The first thing to be done is to measure the noise level in octave bands. And what do I have to do to implement this kind of control?Ī. This is what we call “engineering noise controls” and is considered the best way of reducing the noise exposure of workers. This can be done either by controlling the noise generated by the source or by controlling the path followed by this energy. You can reduce the noise energy reaching your workers.You can provide your workers with hearing protectors, or.That is what is called administrative noise control, something often difficult to implement You can reduce the time your workers are at this location.Obviously, you have to reduce the noise exposure of your workers and you have three means ways of going around: I know, I know it! The question is what can I do to solve this problem?Ī. Since you are exceeding the limit of 85 dBA, you have also a potential problem with the Ministry of Labour. Then, of course, your workers are at risk of overexposure and of losing their hearing. Because of the nature of the work performed there, the noise is more or less constant all the time and the workers are present during the whole shift.Ī. My first question is, is this noise level constant or did you measured an instantaneous level? I just finished measuring the noise level in my workshop and the result is 93 dBA. Author’s Note: This article is intended mainly for health and safety professionals.
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