Real Ear Measurement: The Most Important Step in Hearing Aid Fitting
Real ear measurement (REM) is the gold standard for verifying that hearing aids are actually delivering the prescribed amplification. Despite being recommended by every major audiology organization, only about 30–40% of fittings include it. This guide explains what REM is, why it matters, and how to find providers who do it.
What Is Real Ear Measurement?
Real ear measurement uses a thin, flexible probe tube inserted into the ear canal alongside the hearing aid. The probe contains a tiny microphone that measures the actual sound pressure level at the eardrum while the hearing aid is running.
This measurement is compared against prescriptive targets (DSL or NAL-NL2) — research-based formulas that specify exactly how much amplification should be delivered at each frequency for a given hearing loss. The audiologist then adjusts the hearing aid until the measured output matches the target.
Why this matters: Every ear canal is different in size, shape, and resonance. Two people with identical audiograms will receive different sound levels from the same hearing aid because of ear canal acoustics. REM accounts for these individual differences. Without it, the fitting is essentially a guess.
The Problem with First-Fit
"First-fit" is the default setting that hearing aid manufacturer software applies based on the audiogram. Many providers accept this without verification. Research reveals significant problems:
- Off-target by 10–15 dB: Studies show manufacturer first-fit algorithms frequently miss prescriptive targets by significant margins, especially in the high frequencies critical for speech clarity
- Systematic under-fitting: Most first-fit algorithms intentionally under-amplify to minimize initial loudness complaints, but this means patients aren't getting the audibility they need
- Brand variation: Each manufacturer's first-fit algorithm produces different results, meaning "best fit" varies unpredictably between brands without verification
- Ear canal effects ignored: First-fit doesn't account for your unique ear canal acoustics, which can shift amplification by 5–10 dB in either direction
The consequence: patients may conclude their hearing aids don't work well, when the real problem is that the fitting was never verified.
What Is Speech Mapping?
Speech mapping is a modern, patient-friendly form of real ear measurement. Instead of displaying abstract frequency response curves, speech mapping shows live speech played through the hearing aids overlaid on the patient's hearing thresholds.
The display clearly shows:
- Soft speech (50 dB): Is quiet conversation audible?
- Average speech (65 dB): Is normal conversation clear across all frequencies?
- Loud speech (80 dB): Is shouting or loud music comfortable (not painfully loud)?
- Maximum output: Does the hearing aid limit dangerously loud sounds?
Speech mapping makes it easy for patients to see their hearing aid performance in real time and understand why adjustments are being made.
REM and Speech-in-Noise Performance
Real ear measurement directly impacts speech-in-noise performance. Here's why:
- Under-amplification of high frequencies reduces access to consonant sounds (s, t, f, th) that are critical for speech clarity in noise
- Over-amplification of low frequencies can mask higher-frequency speech cues, effectively reducing the signal-to-noise ratio
- Proper amplification allows directional microphones to work optimally — they can only help with sounds the patient can actually hear
- The SNR improvements reported in clinical studies (e.g., Phonak's 4.5 dB, Oticon's 4.0 dB) were all measured with REM-verified fittings
Key point: The difference between a verified and unverified fitting can be as significant as the difference between hearing aid brands. A well-fitted mid-tier hearing aid may outperform a poorly fitted premium device.
How to Find a Provider Who Does REM
- Ask directly: "Do you perform real ear measurement or speech mapping as part of every hearing aid fitting?"
- Check provider directories: Dr. Cliff Olson's Best Practice directory and HearAdvisor list providers committed to verification
- Look at their website: Providers who invest in REM equipment usually mention it prominently
- Ask about prescriptive targets: Providers using NAL-NL2 or DSL v5 prescriptive targets are more likely to verify fittings
- Be willing to travel: A verified fitting from a provider 30 minutes away will serve you better than an unverified fitting next door
Frequently Asked Questions
What is real ear measurement?
Real ear measurement (REM) uses a tiny probe microphone in the ear canal alongside the hearing aid to measure the actual sound level at the eardrum. This ensures the hearing aid matches prescriptive targets for your specific hearing loss and ear canal acoustics.
Why don't all audiologists do real ear measurement?
Despite being best practice, only about 30–40% of fittings include REM. Reasons include time constraints, equipment cost, and the assumption that manufacturer first-fit algorithms are accurate enough. Studies show first-fit can be off by 10–15 dB at some frequencies.
What is speech mapping?
Speech mapping is a form of real ear measurement that displays the amplified speech signal on screen in real time, overlaid on the patient's audiogram and target prescription. It visually demonstrates that soft, average, and loud speech are all audible and comfortable.
How do I find an audiologist who does real ear measurement?
Ask directly: "Do you perform real ear measurement as part of every fitting?" Check Dr. Cliff Olson's Best Practice directory and HearAdvisor for verified providers. Providers who invest in REM equipment usually mention it on their website.
Related Articles
Watch: Real Ear Measurement — Why Fitting Matters
A walkthrough of the real ear measurement process and why fitting a hearing aid to prescriptive target can add 1–5 dB of effective SNR benefit.
Covers the REM procedure, speech mapping, prescriptive targets, and why first-fit algorithms often fall short.