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This month we are taking a break from our usual audiological blog topics as recently I have had several people ask me about how noise cancelling (noise reducing) headphones work. What are noise cancelling headphones? Ambient noise can interfere or reduce the sound quality of music coming through headphones. Noise cancelling headphones aim to reduce the amount of unwanted ambient noise heard by the wearer while maximizing their listening experience. Types of noise cancelling headphones? There are two main types of noise cancellation; passive or active. The passive type of noise cancelling headphones aim to reduce ambient noise through sound proofing and physical barriers. Active noise cancelling works by providing additional cuts in background noise through the use of ‘anti-noise’. How do they work? Passive Noise Cancelling Headphones Generally, all headphones provide some degree of passive noise reduction because of their construction and placement on/in the ear. This is known as sound proofing. Typically made from specialized high density sound-absorbing material, the circumaural style of headphones are the best at passively cancelling ambient sounds. Circumaural headphones completely enclose the user’s ears, providing isolation and attenuation of unwanted sounds. Without the assistance of any electronics, the headphones themselves act as a physical barrier to decrease the transmission of sound waves (particularly higher frequencies), thus reducing the noise heard by the wearer. Some drawbacks to purely passive headphones include the weight from the additional sound-absorbing material and the tightness needed to seal the ears. Any additional noise which is able to penetrate through the headphones can be further reduced by active noise cancellation. Active Noise Cancelling Headphones Active noise cancelling headphones typically do provide passive attention for higher frequencies with the added benefit of ‘actively’ cancelling the lower frequency portions of noise as well. This reduces the amount of distracting background noise heard by the wearer (eg air conditioning hum, or traffic), resulting in a more comfortable listening experience even in noisy situations. Through a process known as destructive interference (1), the headphones microphone detects an incoming noise and generates a phase-reversed (180o out of phase) signal of that noise which results in an output signal which exactly cancels out the input noise. Basically, it cancels out the unwanted environmental sounds giving the listener added peace and quiet. Some drawbacks to active noise cancelling headphones include that they draw more power (ie need to be recharged more regularly), can be heavier because of the extra electronics, can reduce audio quality and sometimes gives the feeling of added pressure on the ears. Enjoying your music? Feeling as if you’re not hearing your music as well as you’d like? You may be due for a hearing checkup. Feel free to contact our clinic to arrange an assessment with one of our friendly clinicians. 
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