Do I need one hearing aid or two?

Why we have two ears in the first place

Binaural hearing — using both ears together — is not an accident of biology. The brain extracts specific information from the comparison between what each ear hears:

• Interaural time differences (ITD). Sound from your right reaches your right ear a fraction of a millisecond before your left ear. The brain uses this microsecond-level timing difference to localise low-frequency sound on the horizontal plane.
• Interaural level differences (ILD). Higher-frequency sound is partially blocked by the head before reaching the far ear (the "head shadow" effect). The brain uses the resulting level difference between the two ears to localise high-frequency sound.
• Binaural unmasking / squelch. When speech and noise come from different directions, the brain uses the interaural differences in noise versus signal to mentally "unmask" the speech — an effect that can be worth several decibels of signal-to-noise improvement.
• Binaural summation. The brain combines signals from both ears for improved detection of soft sounds — functionally equivalent to a small loudness boost from using two ears instead of one.

An adult with hearing loss in one ear and a hearing aid in the other ear has restored one input to the brain. An adult with hearing loss in both ears and one hearing aid still has only one usable input to the brain. The second hearing aid does not just provide redundancy — it provides the input the brain needs to do all the work above.

The three concrete benefits of fitting both ears

1. Sound localisation

With one functioning ear, you can hear sound but cannot reliably tell where it is coming from on the horizontal plane. With two functioning ears, the brain uses ITDs and ILDs to localise sound to roughly ±5–10 degrees in good conditions. Practical consequences include: knowing which direction a car is approaching from, finding the person who is speaking to you in a group, and following multiple conversations in a room.

2. Speech-in-noise comprehension

The single most common complaint among adults with age-related hearing loss is following conversation in noisy rooms (see our mumbling article). Binaural fitting helps in three additive ways:

• Binaural summation — modest benefit, perhaps 1–3 dB.
• Binaural squelch — the brain uses interaural differences to suppress noise from one direction while preserving speech from another. Several dB of effective SNR improvement when speech and noise are spatially separated.
• Head-shadow benefit — when noise is on one side and speech on the other, the head partially blocks the noise. A wearer with two hearing aids can use whichever ear has the better SNR.

The aggregate speech-in-noise benefit of binaural over monaural fitting is one of the more robust findings in audiology and is the practical reason most clinicians recommend bilateral fitting for bilateral loss.

3. Prevention of auditory deprivation

Auditory deprivation is the term for the gradual decline in speech understanding that an ear with chronic untreated hearing loss can show over years, even when the audiogram itself does not change. The mechanism is thought to be central: the auditory pathways adapt to reduced input from that ear, and re-fitting it later may yield poorer outcomes than fitting both ears from the start.

The clinical implication is consistent across audiology practice: when hearing loss is bilateral, the right time to fit both ears is when the loss is first identified, not several years later after the worse ear has been left unaided.

When one hearing aid is the right answer

Three situations clearly call for one device, not two:

• Unilateral hearing loss. If one ear has hearing loss and the other ear has normal hearing, you typically need one hearing aid in the affected ear — not two. (For permanent severe loss in one ear, the rehabilitation options expand to CROS/BiCROS, BAHA, or cochlear implant for single-sided deafness; see our one-ear article.)
• One ear is unaidable. If hearing loss in one ear is severe-to-profound and does not benefit meaningfully from amplification, fitting that ear with a standard hearing aid may not help. The better-hearing ear gets the hearing aid; the worse ear may be a candidate for a cochlear implant or alternative device.
• Strongly asymmetric loss with very different needs. Some adults benefit from one device that addresses the more affected ear, with no device on the better-hearing ear when amplification there would degrade rather than improve the outcome.

The cost argument — honestly

The most common reason adults buy one hearing aid for bilateral loss is cost. This is real. A pair of prescription hearing aids in 2026 typically runs $2,500–$6,000 bundled; OTC pairs $200–$2,500. Buying one device for a bilateral loss saves roughly half. The trade-offs:

• If you go with one for cost reasons — choose the ear with the worse hearing (or, if symmetric, your dominant listening side, the side you typically hold a phone), and plan to add the second device when budget allows.
• Consider OTC for both ears rather than prescription for one. A pair of self-fitting OTC hearing aids ($800–$2,500 for the pair) often delivers better functional outcomes than a single prescription device, simply because both ears are receiving sound. The 2024 JAMA Otolaryngology study (De Sousa et al.) found self-fit OTC outcomes comparable to audiologist-fit for mild-to-moderate loss.
• Apple's AirPods Pro Hearing Aid Feature at $249 — if you have a compatible iPhone — is a binaural device by design. It is the cheapest path to bilateral amplification currently available. See our AirPods article for limitations.
• HSA / FSA dollars and Medicare Advantage hearing benefits reduce out-of-pocket cost for a pair more than for one device. See how much do hearing aids cost and does Medicare cover hearing aids?

Common objections — addressed

"I only have trouble hearing on one side, so I only need one."

Possibly true if your audiogram shows hearing loss in only one ear. Often not true if it shows symmetric loss but you "feel" it more on one side — many adults are unaware of bilateral loss because it is symmetric. The audiogram is the source of truth.

"Two hearing aids will be twice as loud."

No. Modern hearing aids are fit to your audiogram and compensate for your specific hearing loss. Two correctly fit hearing aids provide the appropriate amplification for both ears — not double amplification.

"I'll get used to one, then add the second later."

This is the auditory deprivation concern. For adults who later add a second device after years of single-ear amplification, integration is sometimes more difficult than fitting both at the start. If you plan to eventually go binaural, sooner is generally better.

"My partner has only one hearing aid and is fine."

Some adults do fine with one device. The evidence is statistical — on average, binaural fitting outperforms monaural for bilateral symmetric loss in speech-in-noise tasks, localisation, and long-term auditory function. Individual mileage varies, particularly in quiet environments.

The decision framework

If your audiogram shows:

• Bilateral, roughly symmetric hearing loss → two hearing aids is the evidence-supported default. Reach for two even if it means choosing OTC over prescription for budget reasons.
• Bilateral hearing loss with notable asymmetry → two hearing aids, but each programmed to its own ear's profile. May still be appropriate to fit both even if one ear is much worse.
• Unilateral hearing loss (one ear normal, the other affected) → one hearing aid in the affected ear. If the affected ear is severely or profoundly deaf, consider CROS, BAHA, or cochlear-implant evaluation.
• One ear unaidable → one hearing aid in the better-hearing ear; consider implant options for the unaidable ear.

The bottom line

The "one or two" question has a clean answer for adults with bilateral hearing loss: two. The reasons are physiological (binaural summation, squelch, head-shadow benefit, sound localisation) and longitudinal (preventing auditory deprivation). The right way to handle the cost trade-off is not "one prescription device" but "two devices in the right category for your budget," which in 2026 includes a real OTC option and the $249 AirPods Pro option for compatible iPhone users. For one-sided loss, one device is appropriate, with the rehabilitation options for permanent single-sided deafness covered in our one-ear article.

Related research

Specific Case

Hearing Loss in One Ear

Causes, workup, and treatment options for unilateral and asymmetric hearing loss.

Audiology Basics

How to Read an Audiogram

How an audiogram reveals symmetry between the two ears.

Cost

How Much Do Hearing Aids Cost in 2026?

Ways to afford two devices, including OTC and HSA/FSA paths.