Is this hearing protection?
There is a common conception that noise-cancelling headphones protect you from dangerous noise. Unfortunately, that isn’t always the case.
Is noise what you think it is?
Noise is sometimes defined as unwanted sound, where one person’s subjective experience of a sound might differ from another. It is also contextual – a loud conversation between colleagues in an open office environment might be noise to you when you are trying to concentrate on a task. The noise many headphones purport to cancel however, is mostly static and periodic, like the droning of an airplane engine or the hum of an air-condition.
Loud sound can be damaging to our hearing, even if it is desirable (like music). How damaging sound is, depends on the level and time we are exposed. When exposure exceeds 85dB for 8 hours a day, you are at risk of acquiring Noise Induced Hearing Loss (NIHL). The time you can safely be exposed to louder sounds, is much shorter. At 100dB, the level of a rock concert, the safety threshold is only 15 minutes.
Potentially damaging sound is not necessarily the same as unwanted sound. The problem is that people are not able to determine if they are exposed to only unwanted or damaging sound. Therefore, many users that have noise-cancelling headphones use this as hearing protection, but it could be false protection!
How does noise-cancelling work?
Active Noise Control (ANC) is often referred to as noise cancellation or noise reduction. In headphones, typically a microphone picks up ambient noise and the opposite waveform of the noise is played back through the speaker, reducing those sounds. Unfortunately, this technique is most effective at the lower ends of audible spectrum that we humans perceive as bass. ANC does not work that well on impulsive sounds or sounds that vary a lot over time, such as the impact of a hammer or speech.
Noise-cancelling systems only achieve a partial reduction of low frequencies, usually around 20dB. Therefore, using the term “cancellation” is an exaggeration. High-frequency noise is typically more dangerous and annoying, but headphones rely on passively blocking the sound out in this range – the ANC doesn’t have any effect in reducing this noise!
Danger, you say?
Consumer-targeted noise-cancelling headphones are not designed to be tested or certified as hearing protection. Still, it is not uncommon to see them used in industrial or noisy settings. CE marked hearing protection has been through testing on humans to make sure that most people wearing it will achieve a certain level of protection, and have high standards for fitting instructions presented to the user. The packaging is marked with a standardized reduction rating, typically an SNR and, or, NRR rating. The typical noise-cancelling earphones will not have gone through this testing, and the effectiveness is uncertain.
Noise-cancelling headphones reduce sound more than open or semi-closed headphones, and there is not the same need to playback at high levels to drown out ambient noise. Still, it is quite possible to do so, and most people don’t have the insight into what is actually damaging levels or how long it is safe to listen to music. As it happens, the false sense of security may even motivate users to play louder music for longer stretches of time, which will elevate the risk of NIHL.
But if I’m completely isolated, I’m safe, right?
Imagine wearing over-the-ear headphones with a tight seal and an effective noise reduction: Yes, your hearing is protected from outside noise. Even though they aren’t certified as hearing protection, they would probably function as one. But being isolated from your environment puts you in real danger in other ways. There are cues in our sound environment that are essential for our spatial and situational awareness, like the sound of a vehicle approaching. Isolation by noise-cancelling technology may be even more disorienting, as they are disproportionately removing some sounds over others.
Many products are now implemented with hear-through functionality, amplifying the sound environment instead of reducing it. However, the microphones, signal processing and loudspeakers have their limitations. The latency (timing), dynamic range (range of hearable levels) and frequency response (audible range from bass to treble) of the audio system don’t allow for an accurate representation of the sound environment. These limitations impede the users ability to determine sound source direction and distance, and the result is an unnatural experience.
So…. what to do then?
Noise-cancelling technology is great for blocking out annoying noise sources like engines and ventilation. It is wonderful to be able to enjoy music without disturbances in noisy environments like on public transportation. However, using earplugs certified as hearing protection is the recommended way to go if you want to protect yourself while:
· still being able to communicate
· be aware of your surroundings
· enjoy live music to its fullest
Unsure if you are in a loud environment that requires hearing protection? Stay tuned for our Industry product to be launched in 2021 with smart noise exposure alerts.