DESIGN AND EVALUATION OF PORTABLE PSYCHOACOUSTIC TESTING SYSTEMS

There is an increasing demand for developing portable psychoacoustic testing systems to evaluate the hearing abilities of people. In this thesis, the design, development, and evaluation of portable, flexible, and versatile wired and wireless psychoacoustic testing systems will be presented. The design of the wired system utilizes a USB audio I/O controller chip for communicating with the application software on the host through a USB cable. The wireless system includes two units: a transmitter and a receiver. 2.4GHz RF transceiver chips are employed for wireless communication. Double-side PCBs populated with 0603 SMD were designed and fabricated. To go along with the hardware, software was developed on a handheld device to control and execute several psychoacoustic tests and to log subjective data. Objective measurements and small scale clinical trials were undertaken to test the efficiency of the proposed portable systems

Psychoacoustic measurements of bone conducted sound

Bone-conduction hearing aids (BCHAs) are a widely used method of treating conductive hearing loss, but the benefit of bilateral implantation is severely limited due to interaural cross-talk. In theory two BCHAs could deliver improved stereo separation using cross-talk cancellation. Sound vibrations from each BCHA would be cancelled at the contralateral cochlea by an out-of-phase signal of the same level from the psilateral BCHA. In order to achieve this the phase and level of sound at each cochlea needs to be known. A method to measure the level and phase required for these cancellation signals was developed and cross-validated with a second technique that combines air- and bone-conducted sound in normal hearing subjects. Levels measured with each method differed by <1 dB between 3-5 kHz. The phase results also corresponded well for the cancelled ear (11° mean difference). The newly developed method using only bone transducers is potentially transferable to a clinical population. To demonstrate cross-talk cancellation tone and speech reception thresholds (TRT and SRT) were investigated with and without unilateral cross-talk cancellation. Band limited noise was emitted from one BT whilst signal +/- cancellation signal was produced by the other. Benefits of cross-talk cancellation under this atypical listening situation were found to be 12.08 and 13.7 dB for TRT and SRT thresholds. In order to estimate the potential benefits of cross-talk cancellation in spatially realistic environments, phase and level elements of impulse responses from a BAHA 4 were convolved with speech. This found that cross-talk cancellation had the potential to lower SRTs in a clinical population by approximately 4.4 dB. Future work will focus on real-time processing and examine using a clinical population

Prevalence and characteristics of tinnitus after leisure noise exposure in young adults

The main goal of this study was to assess the prevalence and characteristics of tinnitus among students after exposure to leisure noise. In addition, the effects of tinnitus on otoacoustic emissions (OAEs) in participants suffering from chronic tinnitus were evaluated. The study consisted of two parts. First, a questionnaire regarding leisure noise exposure and tinnitus was completed. Second, the hearing status of the subjects suffering from chronic tinnitus was evaluated and compared with a matched control group (CG). Furthermore, the psychoacoustical characteristics of their tinnitus in the chronic tinnitus group (TG) were established. The questionnaire was answered by 151 respondents. Seven persons suffering from chronic tinnitus were examined further in the second part of the study. Transient tinnitus was observed in 73.5% of the respondents after leisure noise exposure and 6.6% experienced chronic tinnitus. Transient and chronic tinnitus had similar characteristics, as established by the questionnaire. The amplitude of transient evoked otoacoustic emissions and distortion product otoacoustic emissions was reduced and the amount of efferent suppression was smaller in the TG as compared with the CG. Tinnitus induced by leisure noise is observed frequently in young adults. The characteristics of tinnitus cannot predict whether it will have a transient or rather a chronic nature. In subjects suffering from tinnitus, subclinical damage that cannot be detected by audiometry can be demonstrated by measuring OAEs. These findings underpin the importance of educating youth about the risks of noise exposure during leisure activities

Prediction of effects of noise on man

Quantitative prediction of human effective perceived noise intensitie

Thinking Inside the Box: A New Integrated Approach to Mixed Music Composition and Performance

The Thinking Inside the Box project (TItB) seeks to address pragmatic concerns inherent to mixed music performance, and proposes ways to better consider the sound of the acoustic reality of the concert space at studio composition time. This is achieved through empirical investigation into subversive use of recent developments in hardware and software technologies. The primary concerns are (1) optimising the integration of live instruments and electroacoustic sound in the concert hall environment for both the performers and the public, by carefully choosing loudspeaker types and placement at commission time, and by avoiding sound reinforcement; (2) minimizing for studio composers the insitu trauma of the first live rendition of the piece, by bringing the concert hall acoustic environment into the studio composition process, using convolution reverb to reproduce in the studio the given loudspeaker setup through its impulse responses. This paper presents the conclusions of the project's early experiments in the form of three case study sets, and describes how this approach will be of use for any composer of mixed music

Alterations in Event Related Potentials (ERP) Associated with Tinnitus Distress and Attention

Tinnitus related distress corresponds to different degrees of attention paid to the tinnitus. Shifting attention to a signal other than the tinnitus is therefore particularly difficult for patients with high tinnitus related distress. As attention effects on Event Related Potentials (ERP) have been shown this should be reflected in ERP measurements (N100, phase locking). In order to prove this hypothesis single sweep ERP recordings were obtained in 41 tinnitus patients as well as 10 control subjects during a period of time when attention was shifted to a tone (attended) and during a second phase (unattended) when they did not focus attention to the tone. Whereas tinnitus patients with low distress showed a significant reduction in both N100 amplitude and phase locking when comparing the attended and unattended measurement condition a group of patients with high tinnitus related distress did not show such ERP alterations. Using single sweep ERP measurements the results of our study show, that attention in high tinnitus related distress patients is captured by their tinnitus significantly more than in low distress patients. Furthermore our results provide the basis for future neurofeedback based tinnitus therapies aiming at maximizing the ability to shift attention away from the tinnitus. © 2008 The Author(s)

Microphone and Loudspeaker Array Signal Processing Steps towards a “Radiation Keyboard” for Authentic Samplers

To date electric pianos and samplers tend to concentrate on authenticity in terms of temporal and spectral aspects of sound. However, they barely recreate the original sound radiation characteristics, which contribute to the perception of width and depth, vividness and voice separation, especially for instrumentalists, who are located near the instrument. To achieve this, a number of sound field measurement and synthesis techniques need to be applied and adequately combined. In this paper we present the theoretic foundation to combine so far isolated and fragmented sound field analysis and synthesis methods to realize a radiation keyboard, an electric harpsichord that approximates the sound of a real harpsichord precisely in time, frequency, and space domain. Potential applications for such a radiation keyboard are conservation of historic musical instruments, music performance, and psychoacoustic measurements for instrument and synthesizer building and for studies of music perception, cognition, and embodiment