Probe Tube Microphone Measurements Basics and Definitions Greg

Probe Tube Microphone Measurements (Basics and Definitions) Greg Nassar MCHAS Team University of Manchester

Prescriptive Targets Probe Tube Microphone Measures Best Fit within Fitting Software 2 cc Coupler Individual ear canal size Individual ear canal acoustics Kemar Targets Based on Pure Tones Different Input levels Targets based on Speech

Probe tube Measurement microphone Reference microphone Supporting wire

Umbo Light Reflex Probe Tube

ULL HTL

Real Ear Unaided Response

Clinical measurement of Real Ear Unaided Response (REUR)

REUR The SPL as a function of frequency in the unoccluded ear canal. Is expressed as either SPL or gain in d. B relative to the stimulus level. Real Ear Unaided Response

REUR The SPL as a function of frequency in the unoccluded ear canal. Is expressed as either SPL or gain in d. B relative to the stimulus level. Real Ear Unaided Response

Real Ear Aided Response REUR The SPL as a function of frequency in the unoccluded ear canal. Is expressed as either SPL or gain in d. B relative to the stimulus level. REAR The SPL as a function of frequency in the ear canal with the hearing aid in place and turned on. Also known as in situ response and is normally displayed as d. B SPL Real Ear Unaided Response

Real Ear Aided Response REUR The SPL as a function of frequency in the unoccluded ear canal. Is expressed as either SPL or gain in d. B relative to the stimulus level. REAR The SPL as a function of frequency in the ear canal with the hearing aid in place and turned on. Also known as in situ response and is normally displayed as d. B SPL Real Ear Unaided Response

Real Ear Aided Response REUR The SPL as a function of frequency in the unoccluded ear canal. Is expressed as either SPL or gain in d. B relative to the stimulus level. REAR The SPL as a function of frequency in the ear canal with the hearing aid in place and turned on. Also known as in situ response and is normally displayed as d. B SPL Real Ear Unaided Response

Clinical measurement of real ear aided response (REAR)

Real Ear Unaided Response

Real Ear Unaided Response

Open Ear Gain

Insertion Gain Open Ear Gain

Insertion Gain Target Insertion Gain Open Ear Gain

Insertion Gain Target Insertion Gain Open Ear Gain In adults the REIR is the measure of choice in verifying the electroacoustic characteristics of the chosen hearing aid meet the prescribed gain and desired frequency response. The difference in d. B as a function of frequency between the REUR and the REAR (REIR=REAR-REUR). The real ear insertion gain is the value in d. B of the REIR at a specific frequency

PTM’s on Children REAR should be used rather than REIR. The REAR will prescribe the same gain at the eardrum for a given hearing loss, regardless of ear canal size and shape. This ensures target speech levels at the child’s eardrum will meet the requirements of the hearing impaired ear despite changes in resonant frequencies of the child’s ear canal over the first few years of life.

RESR Is the SPL as a function of frequency in the ear canal with the hearing aid in place and turned on. The measurement is obtained with the stimulus level sufficiently intense as to operate the hearing aid at its’ maximum output level. ULL RECD HTL Is the difference in d. B as a function of frequency between the outputs of a hearing aid measured in the real ear versus a 2 cc coupler. Using these measurements the real ear performance of the hearing aid can be predicted.

Key Points to Take Away! REIG target based upon the average adult ear canal resonance Not appropriate to ear canal with different acoustic properties to average adult ear REAR target based upon the desired SPL at the eardrum This is always the same for a given hearing threshold (d. B SPL) regardless of the size of the ear canal…. . However the output of the hearing aid still needs to be corrected for differing ear canal sizes