We often get asked about earphone and headphone safety here at the HiFi Headphones store.
The question is, are in-ear headphones safe, and do they cause hearing loss or damage? Especially of concern is the safety of children if they listen with earphones for long periods of time.
In-ear sound isolating earphones (also known as ear canal earphones or in-ear monitors - IEMs) create a seal within the ear canal that blocks out external noise. The concern is whether ear canal earphones cause sound pressure levels that are too high and therefore cause hearing damage. Below is our opinion on the subject.
Poor Fitting Ear Buds
If you listen with badly fitting earbuds, such the standard iPod ear buds, then there is a tendency to increase volume to drown out external noises. This means you are exposing your ears to unnecessarily high sound pressure levels.
If you wear correctly fitted ear canal headphones that seal out external noise you have a lower volume delivered to your ear drum as you are not competing with the external noise.
De-Sensitisation Of Your Ears
A good way to illustrate this is the example of listening to the radio while driving a car on a long journey. Because of the external road noise you gradually turn the volume up and up to drown it out. The following day you come back to your car parked on the street, turn the key and get quite a shock when you hear how loud the radio is. While you were driving the previous day your ears became de-sensitised to the increases in volume level. This is what happens with poorly fitting earphones.
Air Tight Seal - does it create too much pressure?
So, if it's true that ear canal earphone form an "air-tight seal" then surely no matter what level the volume is the pressure between the earphone and the ear membrane has nowhere to release itself and is, therefore, dangerous to the fragile ear membrane?
No, not at all. Your eardrum experiences pressure differences all the time - that's how it works! When a sound wave hits your eardrum, it causes a momentary increase in air pressure on that side of the eardrum, which causes the eardrum to move and the volume of the sound you hear is proportional to the pressure. Your eardrum can't tell whether the pressure it experiences is due to a speaker 3 metres away or an earphone transducer 1cm away, and it doesn't really matter - the only real difference is that the transducer is only having to move a very small volume of air to get the same effect as the speaker moving a very large volume of air.
If you were to seal a full size bass driver in an airtight seal to your eardrum and turn that on then yes, you could massively over pressurise the eardrum - but the miniature transducer in an ear canal earphone only moves tiny distances by comparison, and so it only introduces tiny changes in pressure.
Headphone Safety Summary
Exposure to high sound pressure levels for any period of time can permanently damage your hearing. Obviously you should always take care when listening with headphones or earphones. Many famous musicians have admitted that they have permanently damaged their ears by listening to headphones in studios for extended periods of time at unnecessarily high volume levels.
Our opinion is that a good quality set of ear canal earphones that fit well are safer than a poorly fitting set of standard iPod ear buds.