Auditory masking happens when the perception of one sound is affected by the presence of another sound.
The amount of masking that can occur will vary depending on the characteristics of both the target signal (the sound you want to hear) and the masker (the sound you do not want to hear). It is also specific to an individual listener.
Simultaneous masking occurs when a sound is made inaudible by a noise or unwanted sound of the same duration as the original sound. For example, two tones at 440 and 450 Hz can be perceived clearly when separated. They cannot be perceived clearly when presented at the same time.
If two sounds of different frequencies are played simultaneously, two separate sounds can be heard rather than a combination of both. The ability to tell different frequencies apart is known as frequency resolution. When signals are perceived as a combination of both tones, they reside within the same critical bandwidth. This happens due to filtering within the cochlea, the hearing organ in the inner ear. A complex sound is split into different frequencies.
The cochlea is coated with hair cells which spiral along the entire length of the cochlea. The hair cells positioned at the start of the spiral are designed to (de)code high frequency sounds. At the top of the spiral, the hair cells are sensitive to low frequency sounds. Thanks to this mechanism different frequencies can be coded independently onto the auditory nerve. The auditory nerve transmits sound information to the brain. This independent coding only occurs if the frequencies are different enough from each other. If they are to similar they will reside within the same critical bandwidth. This causes the frequencies to be coded at the same spot inside the cochlea resulting in two sounds that are perceived as one instead of two.
Damage to the cochlea and the hair cells in the cochlea can impair the ability to tell sounds apart. This explains why someone with hearing loss would have more difficulty than a normal hearing person in distinguishing between different consonants in speech.
Adjust for masking frequencies
Sound frequencies at the workplace can interfere with your ability to understand speech. If the interfering sound is to loud, you can attempt to reduce the overall volume. Speech, on it’s own, is quite resistant to many masking frequencies. However, different types of work-related (and especially loud) noises can cause frequencies to overlap each other. This overlap can result in a decrease in phonetic information and eventually uncomprehensive speech. Sound filters, used in earplugs and hearing protection, are selected based upon the specific situation, noise levels and sound frequencies in which the earplugs will operate.
The ability to choose the right filter for the right kind of circumstances enables the wearer to hear ‘better’ when wearing the protective equipment compared to when they are not wearing this safety precaution. For example, frequencies that interfere with the ability to distinguish alarm signals from background noise, can be filtered out in order to make these alarm signals more audible to the user.
edited by: Elacin