Sound transmission to the eardrum from various points in the external ear was measured by means of probe microphone technique. Twelve human subjects participated, and three directions of sound incidence were included. For the major part of the audio frequency range the transmission to the eardrum proved independent of direction from points at the centerline of the ear canal, including the entrance (open or blocked). The results further suggested that the region with independent transmission extends some millimeters outside the entrance plane. The transmission from the free field to the eardrum was divided into a directional-dependent part and two directional-independent parts: (1) the transmission from the free field to the blocked entrance, (2) a pressure division between the radiation impedance and the ear-canal input impedance, and (3) the transmission along the ear canal. All parts of the transmission were seen to be highly individual. The first part was shown to be uncorrelated with any of the other parts, whereas mutual dependence of parts (2) and (3) resulted in a smaller variation in the combined transmission than for the parts in separate. The standard deviation between subjects for head-related transfer functions (HRTFs) measured at the eardrum, the open entrance, and the blocked entrance was studied, and the lowest values were found for the blocked-entrance HRTFs. It is concluded, that the blocked entrance is the most suitable point for measurements of HRTFs and for binaural recordings, since sound at this point includes the complete spatial information, and in addition to that the minimum amount of individual information.

Primarily to understand whether clinically relevant factors affect the International Outcome Inventory (IOI-HA) scores and to examine if IOI-HA scores improve when renewing the hearing aids (HA) fo...

When distortion product otoacoustic emissions (DPOAEs) are measured with a high-frequency resolution, the DPOAE shows quasi-periodic variations across frequency, called DPOAE fine structure. In this study the DPOAE fine structure is determined for 50 normal-hearing humans using fixed primary levels of $L_1∕L_2=65∕45\mathrm{dB}$ . An algorithm is developed, which characterizes the fine structure ripples in terms of three parameters: ripple spacing, ripple height, and ripple prevalence. The characteristic patterns of fine structure can be found in the DPOAE of all subjects, though the DPOAE fine structure characteristics are individual and vary from subject to subject. On average the ripple spacing decreases with increasing frequency from $\frac{1}{8}$ oct at $1\mathrm{kHz}$ to $\frac{3}{32}$ oct at $5\mathrm{kHz}$ . The ripple prevalence is two to three ripples per $\frac{1}{3}$ oct, and ripple heights of up to $32\mathrm{dB}$ could be detected. The 50 normal-hearing subjects were divided into two groups, the subjects of group A having slightly better hearing levels than subjects of group B. The subjects of group A have significantly higher DPOAE levels. The overall prevalence of fine structure ripples do not differ between the two groups, but are higher and narrower for subjects of group B than for group A.

To investigate the effect of hearing aid (HA) intervention on long-term health-related quality of life (HRQoL) changes in first-time and experienced HA users using the 15D questionnaire. Secondly, the study explored the relationship between clinical parameters and changes in 15D scores. A prospective observational study. The study population included 1562 patients (1113 first-time and 449 experienced HA users) referred for HA rehabilitation. All patients responded to the 15D at baseline, two months after HA fitting, and at long-term follow-up (698 ± 298 d). Among both first-time and experienced HA users, significant improvements in hearing-dimension (15D-3) score were observed at two-month follow-up which sustained at long-term follow-up. 15D total scores significantly decreased at long-term follow-up. Self-reported hearing abilities, word recognition scores, and HA use time were significantly and positively correlated to increased 15D. Both groups of HA users reported improved hearing-related QoL after HA treatment which sustained at long-term follow-up but the improvement in total 15D total score did not sustain for either group. The results suggest that HA intervention positively affects hearing-related QoL among older adults with hearing loss, and the findings support the use of 15D as a tool for the evaluation of HA treatment effects.

The effects of overexposure on the properties of distortion product otoacoustic emissions (DPOAEs) are investigated. In total, 39 normal-hearing humans were monaurally exposed to a 1-kHz tone lasting for 3min at an equivalent threshold sound-pressure level of 105.5dB. The effects of overexposure were studied in two experiments (1) on the broadband DPOAE and (2) on the DPOAE fine structure, measured using a higher frequency resolution in a narrower frequency range. The obtained DPOAE shifts were compared to temporary threshold shift (TTS) obtained after a similar exposure. Similarities between DPOAE shifts and TTS were found in the affected frequency range and the time course of recovery. The amount of TTS was higher in the early recovery time (1–4-min postexposure), but similar to the DPOAE shift (even in absolute terms) at later recovery times (5–20-min postexposure). The DPOAE fine structure was not systematically changed after the exposure.