We have conducted a comparison of three DPOAE protocols, testing cubic 2F₁ - F₂ distortion products, in order to define the most feasible protocol for a universal hearing screening program. The protocols used asymmetrical stimulus intensities ( L1 > L2) with a frequency ratio of 1.22, in the following format: : (P1), L₁= 60, L₂= 50 dB SPL; (P2), L₁= 65, L₂= 55 dB SPL; and (P3), L₁= 75, L₂= 65 dB SPL. Linear TEOAE responses evoked by click stimuli of 75 dB p.e. SPL were used as controls of the normal cochlear function. Five 2F₁ - F₂ frequencies (ref. to F₂) 1.5, 2.0, 3.0, 4.0, 5.0 kHz were tested with a ILO-92 macro subroutine. The project included randomly selected recordings from 1200 well-baby nursery (WBN) infants (age 48 hr) and 50 very low birth weight NICU infants. Statistical analyses comparing the signal to noise ratios (S/N), at the predefined F₂ frequencies, indicated that the P1 and P2 DPOAE protocols perform similarly. Significant S/N differences were observed in the P3 to P2 and P3 to P1 data-set comparisons. DPOAE scoring criteria were estimated from the P3 data-set, using one-sided distribution-free tolerance boundaries. The scoring criteria for a "pass" were estimated as a minimum S/N of 6.0, 7.0 and 6.0 dB at 2.0, 3.0 and 4.0 kHz respectively. In terms of feasibility, the P3 protocol generated responses in 98% of the WBN and 76% of the NICU infants. All three DPOAE protocols demonstrated smaller time-recording requirements than the TEOAE standard. The false-positive ratio for the NICU infants was estimated as 8%.

Keywords: OAEs, transient otoacoustic emissions, distortion product otoacoustic emissions, TEOAEs, DPOAEs, linear TEOAE protocol, well babies, NICU infants, universal hearing neonatal screening

Noise measurements conducted in selected schools in Gdansk area are presented in this paper. The main aim of this research was to determine noise threats at schools. Some objective measurements of the acoustic climate were performed employing a noise monitoring station engineered at the Multimedia System Department, Gdansk University of Technology. Simultaneously, subjective noise annoyance examinations were carried out among pupils in chosen schools. The survey includes a noise analysis in places of residence, music preferences and preliminary hearing tests results taken after the exposure to noise during breaks. Hearing tests employing a distortion product otoacoustic emission (DPOAE) method, have been performed twice -- before and after the exposure to noise. The noise dose analysis based on average time spent by a pupil at school is also presented. The obtained results reveal that an unfavorable noise climate occurred in surveyed schools. This was also confirmed by the results of the subjective examinations. The conducted hearing tests did not reveal essential changes in the cochlea activity of examined pupils. This means that the noise during breaks and physical exercises did not constitute a risk to their hearing system. However, it may be considered as an essential source of annoyance.

Keywords: noise measurement, hearing, noise at school

The proposed contactless hearing aid is designated to be attached to the infant’s crib for sound amplification in a free field. It consists of 4 electret microphone matrix, and a prototype DSP board. The compressed speech is transmitted and amplified via miniature loudspeakers. Algorithms that are worked out deal with parasitic feedback, which occurs due to the small distance between microphone and monitors and potentially high amplification required. The beamforming algorithm is based on an artificial neural network (ANN). The ANN is used as a nonlinear filter in the frequency domain. Principles of algorithms engineered and the prototype DSP unit design are presented in the paper. Also, results of experiments simulating the real-life conditions are analyzed and discussed.

Keywords: hearing aid

While fitting process of modern hearing aids hearing dynamics characteristics is required. The hearing dynamics characteristics is calculated on the basis of loudness scaling test results. The problem is that the loudness scaling test results are represented on a loudness category scale, but a hearing aid requires numerical parameters. A fuzzy logic method is the one of the simplest artificial intelligence methods which is useful for processing parameters expressed in a human natural language. In this article the fuzzy system for loudness scaling result processing is presented. Additionally, the method for shortening loudness scaling test is explained.

Keywords: fuzzy logic, loudness scaling