Hearing aids amplify sound for individuals experiencing hearing loss. A common question is whether a single device is sufficient, or if a pair is required for optimal results. The decision between using one hearing aid (monaural) or two (binaural) depends on the individual’s specific hearing profile, the characteristics of their hearing loss, and how the brain processes sound. For those with measurable hearing loss in both ears, the benefits of utilizing two devices generally far outweigh using only one.
The Science of Binaural Hearing
The human auditory system is naturally designed to function with input from two ears, a process known as binaural hearing. This dual input allows the brain to make sense of the acoustic environment in ways a single ear cannot. The brain uses subtle differences in sound reaching each ear to achieve two primary functions: sound localization and improved clarity in noise.
Sound localization, the ability to pinpoint the origin of a sound, relies on comparing differences in the timing and intensity of sound waves arriving at both ears. The head creates a “shadow” that makes high-frequency sounds slightly louder in the ear closest to the source, known as the interaural level difference (ILD). For lower-frequency sounds, the brain analyzes the interaural time difference (ITD), which is the minuscule delay in arrival time between the two ears.
Binaural processing also significantly enhances the signal-to-noise ratio (SNR), the relative level of desired sound compared to background noise. By combining and comparing signals, the brain can effectively filter out distracting noise, making it easier to focus on conversation in a crowded room. This natural teamwork allows a person to hear sounds from a wider 360-degree field, which is not possible with only one functioning ear.
Key Advantages of Binaural Amplification
When two hearing aids treat bilateral hearing loss, this binaural amplification restores the natural advantages of having two ears. A noticeable benefit is a marked improvement in speech discrimination, particularly in complex or noisy listening environments. The paired devices work together, allowing the brain to utilize natural cues to separate speech from competing background sounds.
Using two aids results in a more balanced and natural sound quality, avoiding the feeling of sounds being one-sided. Because the auditory workload is shared between both devices, each can operate at a lower overall volume setting while still providing clarity. This reduced amplification can lead to less distortion and a smoother, more comfortable listening experience.
This cooperative function helps reduce listening fatigue, a common issue for individuals with untreated hearing loss. When the brain receives insufficient or imbalanced auditory input, it must strain harder to fill in missing information, consuming cognitive energy. By providing simultaneous, clear input to both sides, binaural amplification lowers the cognitive load required for listening, making social interactions and prolonged conversations less tiring.
When a Single Hearing Aid is Recommended
While binaural fitting is standard for most individuals with hearing loss in both ears, a single hearing aid may be appropriate in specific circumstances. The clearest instance is unilateral hearing loss, where a person has normal hearing in one ear but a measurable loss in the other. In this case, only the impaired ear requires amplification to restore balance and improve communication.
A monaural fitting may also be considered in cases of profound asymmetry, where one ear has such a severe loss that standard amplification offers minimal practical benefit. Other considerations include certain medical contraindications or in some elderly patients where auditory stimulation from two devices might be overwhelming. However, these situations are generally exceptions to the rule that bilateral loss should be treated bilaterally.
Risks of Treating Only One Ear
Choosing to treat only one ear when hearing loss is present in both carries significant risks, the most prominent being auditory deprivation. Auditory deprivation occurs because the untreated ear, deprived of sound stimulation, gradually loses its ability to recognize and process speech sounds. Over time, even if a hearing aid is later introduced, the brain struggles to interpret the amplified sound.
This effect is a decline in the central auditory processing system’s function for that ear, not just a reduction in sensitivity. When an individual with bilateral loss wears only one hearing aid, the untreated ear’s ability to understand speech can weaken or atrophy. Furthermore, managing bilateral hearing loss with a single device increases cognitive strain, forcing the brain to compensate for missing information. This continuous overexertion is associated with an increased risk of cognitive decline and dementia.