Hi, I’m Gregoire and I’m an engineer here at Electrical Audio.
In this video we’ll learn about sound levels, and how to prevent hearing loss.
[clunk, clunk.]
Alright, let’s take a look at that ear.
Sounds comes in through the ear canal, here, and it travels
to the eardrum. The eardrum is basically like
a microphone, it captures the sounds and vibrates. Behind the eardrum, you've got
three little bones here, the ossicles. They carry the mechanical vibration into the
sensory organ, which is the cochlea, here. The cochlea has two different
kinds of cells: the outer hair cells, which act as a preamplifier, basically, and the
inner hair cells which act as converters. They convert the vibration into electrical
impulses. Then those electrical impulses are carried through the auditory nerve toward
the brain. When you get exposed to loud sounds, most of the time it will be your outer
hair cells that get damaged, so that’s why you will hear softer than before. Sometimes
it is temporary, sometimes it is permanent. When you lose outer hair cells, they do not
regenerate. It is the same with inner hair cells, you are born with so many hair cells
and when they die, it’s gone forever. It’s important to know that and protect
your ears. Now, we’ll talk about how to measure sound levels.
You’ve probably heard of decibels, but there
are many kinds of decibels. For example:
dB SPL,
dB(A),
and dB(C).
The dB scale is not very intuitive.
It is not linear, it is logarithmic.
So, if you have a guitar amplifier
that delivers 90 dB SPL
and you double that setup with the exact same
amplifier, instead of having 180 dB SPL you will only get
93 dB SPL. So it’s very important to use a device
when measuring sound levels, like a
sound level meter or an application on your phone.
[speaking in French] What are dangerous sound levels?
You have three factors you need to consider: the first one is time of exposure, the
second one is distance from the sound source, and the third one is shielding from the
sound source or wearing ear protections. The general consensus is that an exposure of
85 dB(A) over 8 hours can damage your hearing. But you can also cause
equivalent damage by exposing yourself – I should not say exposing yourself.
But you can do as much damage in 15 minutes
if you’re exposed to 100 dB(A).
Let’s head over to the studio and look at the impact of distance.
[WOOSH]
Now we are in studio B
we have Steve on guitar, and we have an amplifier
in the back. I’ll make some measurements using a free app you can all
download on your phone. First I’ll do a measurement close to the amplifier, as if
a studio microphone was put there. Next I’ll do a measurement 3 feet
away, where Steve would typically be playing his guitar. Then I’ll double
that distance to approximately 6 feet away, and we will compare the sound levels measured.
This is an original composition called "E minor and F".
[LOUD GUITAR PLAYING]
And now we’ll do the same thing but with a snare drum and a cymbal.
[LOUD DRUMMING]
Here are a few take-aways from those measurements:
the first one is that when you double the distance from the sound source
you should see a drop of approximately 6 dB
on your sound level meter. Another thing
to note is time of exposure:
if you lower the sound level by 3 dB, you may
double your time of exposure and still be safe,
without damaging your ears.
And the last thing, is that with drums you must be careful with the peak levels, because you
can measure 100 dB(A) on average but if the peak levels are much higher, they
can do damage - much more than you’d think. For example the snare
drum we just measured was peaking at 136 dB SPL.
So wear those earplugs whenever you can.
Now we’ll go back to the control room.
Alright, we just talked about time of exposure
and distance from the sound source, but the most effective way you can
protect your ears is by wearing ear protection. I have a few different kinds here.
It ranges from ear muffs, that can protect your ears up to 30 dB. Noise canceling
headphones, those are best for low frequency sounds like airplanes or machine
noise, they can cancel up to 30 dB as well. Foam earplugs, they can reduce
between 10 to 25 dB, depending on how you fit them into your ears. And custom earplugs,
these ones have the 25 dB filter, but it ranges from 9 dB to 25 dB. One problem
with the foam earplugs is that depending on how you roll them and put them into your
ears, they can protect a lot or not at all.
So I would recommend strongly the custom earplugs, because you know you will get the
same attenuation every time you put them on. As an example:
if you are exposed to 110 dB(A) without ear plugs, you can damage your hearing within 1 minute!
But if you are wearing the 25 dB earplugs you could stay 8 hours without damaging your hearing.
Remember, if you notice a change in your hearing, it could already be too late, so
prevention is the best course of action.
Visit us at www.electricalaudio.com