12Reading the Audiogram to Pick the Device

FEvery device has an audiometric box

The single most powerful skill in this field is learning to look at an audiogram and see, overlaid on it, the indication ranges of the available devices. Each device class is engineered to deliver a certain amount of gain and output, and the manufacturers and regulators translate that capability into an audiometric box: a region of the audiogram inside which the device can be expected to help. A candidate is, at heart, a patient whose audiogram falls inside the right box.

These boxes are read on different axes for different problems. For bone-conduction and middle-ear devices used in conductive and mixed loss, the relevant axis is the bone-conduction threshold, because the device must clear the air-bone gap and still have output to spare. For cochlear implants the relevant measure is severe-to-profound sensorineural loss plus poor aided speech understanding. And for single-sided deafness the boxes are defined by the contrast between a deaf ear and a good ear.

Thinking in boxes prevents the two classic errors: offering a device to an ear that sits outside its range, where it will underperform, and overlooking a perfectly good option because the audiogram was read as a single line rather than as a map of possibilities.[2022][2005]

TThe ranges, device by device

For conductive and mixed loss, bone-conduction implants are broadly indicated up to bone-conduction averages in the region of 45 to 65 dB HL, with the achievable ceiling depending on the transducer’s power and whether the system is passive or an active higher-output design. Active middle-ear implants are fitted against gain targets and have their own published fitting ranges, with the safe boundary best defined by an objective measure of output and dynamic range rather than a single number.

For sensorineural loss too severe for these direct-drive devices, the cochlear implant takes over: the candidacy box is severe-to-profound bilateral sensorineural loss with limited benefit from optimally fitted hearing aids on speech testing, as set out in current task-force candidacy guidelines. Between these zones there is overlap, and the bone thresholds are what decide which side of the boundary a mixed-loss ear falls on.

For single-sided deafness the decision is not a single box but a fork. A deaf ear paired with a good contralateral ear can be managed by rerouting (CROS or bone conduction) or, if the goal is to restore the deaf ear, by cochlear implantation, with candidacy guidelines specifying how deaf the poor ear and how good the better ear must be. The audiometric criterion here is the asymmetry itself, not a single threshold.[2014][2024][2022]

CBeyond the audiogram: trials, anatomy and counselling

An audiogram inside the box is necessary but not sufficient. For bone-conduction devices the most informative step is a trial: a processor worn on a softband (in children) or held on a test rod (in adults) lets the patient and clinician hear the actual benefit before any surgery, and it predicts the result far better than the audiogram alone. This try-before-you-buy step is one of the genuine advantages of bone-conduction technology.

Anatomy then constrains the final choice. A CT scan confirms there is enough bone thickness and quality to seat a bone-conduction implant, that the mastoid and middle ear will accept a middle-ear transducer, and that the cochlea is patent and the cochlear nerve present before a cochlear implant. Malformation, ossification, prior surgery or a deficient nerve can move a patient from one device class to another regardless of the audiogram.

Finally, counselling must be honest about what each option does and does not deliver. Direct-drive devices restore access for an ear that could not otherwise be aided; a cochlear implant restores hearing to a deaf ear; rerouting devices restore awareness but not binaural hearing. Setting these expectations before surgery is what turns a technically correct device choice into a satisfied patient.[2005][2026][2024]

CA worked routine for matching device to ear

Put the framework into a repeatable routine. First classify the loss: sensorineural, conductive or mixed, and whether it is unilateral with a good other ear. Second, plot both air and bone curves and ask which device boxes the ear falls inside. Third, for conductive or mixed ears confirm a standard aid is unusable or has failed, and run a softband or test-rod trial. Fourth, image the relevant anatomy to confirm the chosen device can be implanted.

Only then commit, and counsel to match. A good-bone conductive or mixed ear that cannot wear an aid points to a bone-conduction or middle-ear device; a severe-to-profound sensorineural ear with poor aided speech scores points to a cochlear implant; a single dead ear with a good partner opens the rerouting-versus-implant conversation driven by the patient’s goals around localization and tinnitus. Read the audiogram as a map, layer on the trial and the scan, and the right device usually selects itself.[2022][2024]