İşitmeAtölyesiHearing Aids
Device types, matching the right device to the patient, the fitting process and the basics of care — for students and professionals.
For information: This page is a concise guide for students and professionals; for clinical decisions, device selection and prescription, consult an audiologist / ENT specialist. Information is compiled from NIDCD, ASHA, AAA and FDA sources.
Overview
A hearing aid is a small electronic device with three core parts: a microphone, an amplifier (DSP) and a receiver (loudspeaker). In sensorineural loss it stimulates the remaining hair cells with stronger vibration to make sound audible — it does not cure the loss; it improves audibility.
The journey of sound from device to ear
Microphone
Converts sound waves into an electrical signal.
Amplifier · DSP
Processes the signal individually and amplifies it selectively.
Receiver (loudspeaker)
Delivers the processed sound into the ear canal.
Today's devices are digital: they convert sound into a digital code, personalize it by frequency, can focus in a given direction and can reduce noise. (NIDCD)
Types and styles
The electronics sit in the housing behind the ear; sound is delivered to the ear through a thin tube and an earmold or dome. It is the most versatile type, suiting every degree of loss; the open-fit option leaves the ear canal open.
Suitable loss: mild – profound
- Widest power range
- Easy handling, long battery
- Most features / telecoil
- More visible
- Can be affected by sweat and moisture
A mini BTE; the receiver (loudspeaker) is not in the housing but at the ear tip. It is the most common type today and gives a natural, open sound.
Suitable loss: mild – severe
- Small, discreet
- Natural sound, open fit
- Receiver easily replaceable
- Receiver can be affected by moisture/debris
- Limited in profound loss
A custom-made shell that fills the outer ear (concha). There is room for features such as a telecoil.
Suitable loss: mild – severe
- Easy to insert
- Good battery life
- Room for features
- Visible
- Can cause an occlusion (blocked) feeling
A custom shell that sits at the canal entrance, slightly smaller than an ITE.
Suitable loss: mild – moderate
- Discreet
- Can fit a directional microphone
- Small controls
- Moderate battery life
A nearly hidden device seated deep in the canal.
Suitable loss: mild – moderate (sometimes severe)
- Barely visible
- Low wind noise
- Small battery, harder to handle
- Limited features / telecoil
The device seated deepest in the canal, almost invisible from outside. It does not suit everyone's canal anatomy.
Suitable loss: mild – moderate
- Almost invisible
- Natural ear acoustics
- Hardest to handle
- Most limited power and features
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The shaded area is the region of hearing loss this type/receiver typically fits (milder at the top, more severe lower down). It is illustrative; the real range varies by brand/model and widens or narrows with earmold–venting and feedback management. Source: RIC receiver power classes (S/P/SP) and style fitting-range summaries (Hearing Review, ASHA).
Source: NIDCD, ASHA. Types are chosen by degree of loss, ease of use, cosmetics and feature needs.
At a glance
As size increases, visibility decreases; as it shrinks, power, battery and feature space shrink too.
| Type | Placement | Suitable loss | Visibility | Handling/battery | Feature space |
|---|---|---|---|---|---|
| Behind-the-ear (BTE) | Behind ear + earmold/dome | Mild–profound | Visible | Long battery, easy | Widest |
| RIC / RITE | Behind ear, receiver in canal | Mild–severe | Discreet | Good, easy | Wide |
| In-the-ear (ITE) | Fills the concha | Mild–severe | Visible | Good battery | Wide |
| In-the-canal (ITC) | Canal entrance | Mild–moderate | Discreet | Moderate | Moderate |
| Completely-in-canal (CIC) | Deep in canal | Mild–moderate | Very little | Small battery, hard | Limited |
| Invisible (IIC) | Deepest in canal | Mild–moderate | Almost none | Hardest | Most limited |
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Which device for which hearing loss?
Device selection cannot be reduced to a single rule; mainly the degree of loss, audiogram configuration, type of loss (conductive/sensorineural/mixed) and acoustic coupling (dome/earmold, venting), together with speech discrimination, lifestyle and manual dexterity, are considered together. Answer the steps to see the typical approach.
1 · Degree of hearing loss?
2 · Audiogram configuration?
3 · Visibility / cosmetics?
4 · Dexterity and vision?
5 · Lifestyle and connectivity?
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Reference: degree and configuration
ASHA classification (dB HL) and acoustic-coupling logic by audiogram shape.
| Degree | dB HL | Effect on audibility | Typical device approach |
|---|---|---|---|
| Slight | 16–25 | Quiet/distant speech and soft consonants may be missed | Usually no device required; if needed, open-fit RIC with minimal gain |
| Mild | 26–40 | Difficulty with soft speech and in noise | Any style suitable; often open-fit RIC / RITE |
| Moderate | 41–70 | Even normal-level speech is understood with difficulty | RIC / BTE (closed dome or earmold); ITE / ITC |
| Severe | 71–90 | Even loud speech is hard to hear | Power BTE (with custom earmold) preferred; power RIC |
| Profound | ≥91 | Speech is largely inaudible | Super-power BTE + custom earmold; cochlear implant considered |
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In some classifications 56–70 dB is also called “moderately severe”. Source: ASHA.
| Configuration | What it means | Acoustic coupling |
|---|---|---|
| Flat | Similar thresholds across all frequencies | Balanced gain; closed coupling for moderate and greater loss |
| Sloping high-frequency | Most common; good lows, poor highs | If lows are near-normal, open dome + maximum venting; a candidate for frequency lowering with steep slopes |
| Low-frequency (reverse slope) | Poor lows, good highs (rising) | Closed dome or earmold; an open dome is insufficient |
| Notched (4 kHz) | A single-frequency notch due to noise | Targeted high-frequency gain |
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People with low-frequency thresholds above 40 dB or needing ≥10 dB of low-frequency gain cannot be fitted adequately with open/tulip domes.
How was this section prepared? The degree classification and dB HL ranges are from ASHA; the configuration–acoustic-coupling principles (open/closed dome, venting, occlusion, candidacy for frequency lowering) are compiled from ASHA and the open-fit clinical-practice literature. The wizard maps your chosen degree and configuration to a “typical approach” with a simple set of rules.
Limits and margin of error: This is a simplification, not a real prescription or clinical assessment. Because individual audiogram detail, loss type (conductive/sensorineural/mixed), speech-discrimination score, ear anatomy, feedback and personal preferences are not considered, the suggestions may be incomplete or wrong. For a definitive decision, current clinical guidelines and your audiologist's assessment are essential.
Sources: ASHA — Degree of Hearing Loss · NIDCD — Hearing Aids.
What does the device do? — core features
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Active: WDRC · DSP processing stage
Steady background noise (grey) is suppressed; speech (green) is preserved. NR mostly improves comfort and usually does not markedly change intelligibility.
Pick a sound type, then listen uncompressed and with WDRC and compare the output waveform: soft sounds become audible, loud ones are held back.
⚠ Lower your device volume before listening; these are short, low-level simulations. Approximated with the WebAudio DynamicsCompressor.
Source: NIDCD, ASHA and related signal-processing research. The benefit of features varies by environment and person.
Prescription target and real-ear measurement (REM)
A prescription formula (e.g. NAL-NL2 or DSL v5) sets a target from the audiogram; real-ear measurement (probe microphone) measures the sound reaching the eardrum (REAR) and matches it to that target. A real REM measures at three input levels (soft/normal/loud). The manufacturer's “first-fit” often misses the target — adjust the parameters below to bring the device output closer to the target.
A simplified representation; a real REM measures frequency-specific gain/output at soft–medium–loud inputs and keeps MPO below the discomfort threshold. Source: AAA/ASHA best practice; NAL-NL2, DSL v5.
Formula, verification and validation
Which target it is set to, how you measure whether the fit meets the target, and how real-world benefit is assessed.
NAL-NL2
The most common prescription target in adults. It aims to maximize speech intelligibility at a comfortable loudness.
DSL v5
Preferred especially in children; it tends to provide more audibility for soft sounds.
- Verification: Does the device actually reach the target? With a probe microphone (REM), the output at the eardrum (REAR) is measured and compared to the target — it is objective.
- Validation: Does the person benefit in real life? Assessed with self-report measures such as COSI, APHAB, IOI-HA — it is subjective.
- Manufacturer first-fits often miss the target; therefore verification with REM is recommended.
Source: AAA / ASHA best-practice guidelines; NAL-NL2, DSL v5.
Adapting and expectations
A hearing aid does not restore normal hearing; with regular use, awareness of sounds and intelligibility improve. What to expect in the first weeks:
Occlusion / own voice
In the first days your own voice may sound “blocked”; most people adapt over time.
Gradual use
Start in quiet settings and gradually move to noisier ones.
Realistic expectations
Background sounds do not disappear entirely; the device cannot separate every sound.
Regular follow-up
If whistling, discomfort or own-voice issues persist, see your audiologist for fine-tuning.
Source: NIDCD. For information only.
Connectivity
Technologies that connect the device to phones, TVs and loop systems.
Telecoil / hearing loop
In loop systems such as phones, theatres or mosques it picks sound up directly into the device, overcoming noise and distance.
Bluetooth / streaming
Streams phone, TV and music audio directly to the device; the new LE Audio / Auracast standards are spreading.
Rechargeable
Overnight charging instead of battery changes; practical for people with limited dexterity.
Phone app
Volume/program control, environment selection and, on some models, remote fine-tuning.
Note: Models offering both rechargeability and a telecoil may not be available from every brand.
Battery options: disposable or rechargeable?
Two common options: replaceable zinc-air batteries and a built-in rechargeable (lithium-ion) battery.
Zinc-air battery (disposable)
Single-use batteries replaced as they run out; roughly 5–14 days depending on size.
- Low upfront cost, widely available
- Swapped instantly when depleted; spares are portable
- Possible even in very small/deep devices
- Regular changes; small parts (dexterity)
- Battery waste
- Streaming shortens battery life
Rechargeable (lithium-ion)
A built-in battery charged overnight; usually enough for a full day — about 16–30 hours with heavy streaming.
- No battery changes; easy for limited dexterity
- Ready for the day after an overnight charge
- No waste, eco-friendly
- Needs a charger; no spare if it runs out mid-day
- The battery is fixed; capacity drops over years, replacement is via service
- Not always available in very small (IIC) models
Source: NIDCD, ASHA. Durations vary by device size and use.
Having a problem? Quick check
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If the problem persists, take your device to your audiologist/service. Source: NIDCD.
Implantable alternatives
When amplification is insufficient or the anatomy is unsuitable, surgical/implantable options are considered.
Middle-ear implant (MEI)
A small device attached to one of the middle-ear ossicles; it delivers sound directly to the ossicles rather than the eardrum, boosting vibration.
Bone conduction / BAHA
Attached to the bone behind the ear; it conducts sound through the skull directly to the inner ear, bypassing the middle/outer ear. Used in single-sided deafness or middle/outer-ear problems.
Cochlear implant
When the inner ear (cochlea) is severely damaged; a surgical device that electrically stimulates the hearing nerve directly. Considered in severe–profound loss that does not benefit enough from hearing aids.
Cochlear Implant guide →Because surgery is required, the benefit/risk balance is assessed with a physician. Source: NIDCD.
Device costs, trials and reimbursement
Price is not a single figure; it is set by technology level (basic → advanced), style and features, one/two devices and the cost of service-fitting-follow-up. In Türkiye, SGK covers the cost under certain conditions.
Devices range from hundreds to a few thousand lira/dollars; style and features affect cost — the most expensive is not always the most suitable.
Most manufacturers offer a 30–60 day trial period; ask about return terms, warranty and repair/maintenance coverage in advance.
Two devices for two ears are usually recommended; this raises cost but also increases hearing benefit.
Source: NIDCD; SGK/SUT for Türkiye.
Frequently asked questions
If both ears have loss, two devices are usually recommended: a more natural signal, sound localization and understanding speech in noise.
No. A device does not cure the loss; it improves audibility. It requires regular use and an adaptation period.
For adults with perceived mild–moderate loss, OTC can be an option. Severe/profound loss and those under 18 require prescription devices.
Manufacturer first-fits often miss the target; verification with a probe microphone (REM) is best practice.
It varies by person; with regular use and gradual environment changes, awareness and intelligibility improve within weeks.
Mini glossary
- BTE / RIC / ITE
- Behind-the-ear / receiver-in-canal / in-the-ear device styles.
- WDRC
- Wide dynamic range compression: gain that varies with input (amplifies soft a lot, loud a little).
- REM
- Real-ear measurement: measuring the output at the eardrum with a probe microphone.
- REAR
- Real-ear aided response: the sound level at the eardrum while the device is running.
- NAL-NL2 / DSL v5
- Prescription formulas that set a gain target from the audiogram (adult- / child-oriented).
- Telecoil
- A small coil that picks up sound from loop systems magnetically instead of via the microphone.
- Occlusion
- Hearing one's own voice as “blocked/boomy” when the canal is occluded.
- Feedback
- Sound leaking from the device re-entering the microphone and whistling.
- Dome / earmold
- The tip coupling the device to the ear: a ready-made dome or a custom earmold.
- Venting (vent)
- A hole in the earmold/dome: reduces occlusion, affects low-frequency gain and feedback.
- MPO
- Maximum power output: the loudest sound the device can produce; kept below the discomfort threshold.
Sources
“A hearing aid does not restore your normal hearing; with practice it improves awareness of sounds and their sources.”
NIDCD — Hearing Aids