Photo of saxophones to illustrates sound pressure

The decibel is a unit of measure of sound. Its scale is not linear, it is logarithmic. Therefore, its manipulation is not always very intuitive.

Here are some important rules:

  • We double energy at the sound source when sound is increased by only 3 dB. In this way, two saxophones playing at 60 dB produce a sound of 63 dB and not 120 dB. Conversely, if sound increases by 3 dB (for example in a nightclub) we multiply the sound energy by 2, so the safe listening time is diminished by 2.
  • We multiply sound energy at the source by 10 when we increase the sound by 10 dB.
  • When we combine 2 sources of sound of different intensities, the resulting intensity will be about equal to that of the strongest source. In our example an alto saxophone plays at 60 dB and a tenor sax plays at 70 dB at the same time, producing a combined sound of 70 dB.
  • The sound decreases by 6 dB when doubling the distance from the source.

In addition to these mathematical rules, we must add the particular functioning of our ear and its way of perceiving sound. This is what is called psychoacoustics. In other words we can say that each time that the sound level increases by 10 dB, we hear 2 times louder. In these terms sound of 100 db is heard 4 times louder than sound of 80 dB.

Reference points on the decibel scale

  • 0   dB: Normal hearing
  • 65 dB: Normal level for conversation
  • 80-85 dB: Below risk level for injury
  • 110 dB: This is the limit after which there is a potential  risk
  • 120 dB: Threshold For Auditory pain.

A rock group plays between 85 and 105 dB. These sound levels present a risk for the inner ear, and the risk increases according to increased rates of exposure. Moreover, we are not equal when faced with an auditory trauma, certain people are more sensitive than others.  As a result, not all  band members  who are exposed to the same loud noise will suffer the same consequences as another band member. 

Sound technicians like musicians are subjected to intense sound almost daily, despite the fact that their ears are their main work tools. Therefore, it is important that they take of them and protect them so that they can perform throughout their lives.

Today, more and more  use personal hearing protection with acoustic filters  from 9 to 15 dB.

Although some acknowledge that they don't wear them all the time, they like to wear them when the mix is done and the sound is going on. These filters reach all frequencies in a linear fashion, they provide very good listening quality, but  is not as loud depending on the filter you wear.

It is a little like controlling the volume at the entrance of your ear. You can remove them from time to time to control your mix, but the more you wear them the more you will soothe your ears and preserve your hearing potential the longest time possible.

The acoustic filter is a small round piece that is inserted into a personalized ear Mold. It is fabricated from a Mold of your auditory canal and will reduce some of the sound energy that reaches the auditory canal.

The specificity of the filters used here is that they have linear fade curves, this means that they fade the varying frequencies of the auditory spectrum in the same way. As a result, the sound that exits the filter is the sound that is heard at the entrance to the auditory canal, but at a lower level (Thus reduction depends on the strength of the filter). The quality of the sound is the same but at a sound level that does not take away from your hearing.

It is a bit like having access to the volume of the room. We suggest fade filters of 9Db, 15 dB, and 25 dB, choosing those that are best adapted to your practice.

Apart from a few rare events (volcanic eruptions, tsunami, earthquakes), nature does not expose hearing to high intensity sounds. Our ear did not have to develop a system of protection against loud sounds. The ears have no eyelids! This explains why our auditory system is vulnerable to high-intensity sounds that are generated today in industry, entertainment or with amplified music. The ability of our ear to listen to high intensity sounds without danger depends on the duration of these sounds. Thus, the World Health Organization defines safe exposure times according to the loudness:

 

Daily noise exposure limits (1 meter distance from source)
Sound level in dB(A)    Duration of sound exposure
85 8 h
88 4 h
91 2 h
94 1 h
97 30 min
100 15 min
103 7.5 min

It can be noted that the permissible exposure time decreases by half each time the level increases by 3 dB. This is due to the non-linearity of the dB scale. Beyond 130 dB, ear damage is considered to be extremely dangerous, even for very short exposures.