It sounds like common sense really, the further away from a sound you are, the harder it is to hear it. However, one thing we know as hearing professionals is that our clients find most difficulty hearing speech at a distance in noisy environments, even with the best technology on offer. Why would that be?
Over this article and the next we will cover some points that will go some way to explaining what challenges we come up against when trying to help you the customer hear the best you can in that type of environment.
The first point is this; with sound and distance we must consider the ‘inverse square law’ which dictates that sound level falls by 6dB when the distance travelled by the sound is doubled. For instance if a sound is 60dB SPL at a distance of 1 metre, it will be 54dB SPL at 2 metres and 48dB SPL at 4 metres.
Obviously in real life situations, such as a typical room where sound bounces off surfaces etc things become rather more complicated, but let’s leave that out of the equation for simplicity.
A factor to consider is that there is always a level of background noise, even in a quiet room. If the level of ambient noise is a very low 45dB SPL, once you get more than say 5 metres away speech will start to be muddled in with the ambient background noise and be less distinct.
This difficulty will obviously be more pronounced if you have a degree of hearing loss, even a relatively moderate level of loss.
In the next article in a few days we will cover more points on this subject.