Christopher Barlow

Electrolaryngographically derived voice source changes of child and adolescent singers.

Children are the most likely demographic group to undertake regular singing or singing training, but to date there has been little quantitative research into the voice production of children. The authors used closed quotient (CQ) measurements to analyse the singing voices of over 200 male and female, trained and untrained singers aged 8–18 years for differences in voice source according to sex, vocal training and age. Results indicated that the voice source production of subjects could be clearly divided into groups according to age, sex and the level of vocal training received. It was concluded that the process of training a young voice has a quantifiable effect upon the voice source. It was also concluded that sex differences result in significant differences in the voice source of child and adolescent singers.

Behaviour of ultrasonic waves in porous rigid materials: an anisotropic Biot-Attenborough model

© Published under licence by IOP Publishing Ltd. The anisotropic pore structure and elasticity of cancellous bone cause wave speeds and attenuation in cancellous bone to vary with angle. Anisotropy has been introduced into Biot theory by using an empirical expression for the angle-and porosity-dependence of tortuosity. Predictions of a modified anisotropic Biot-Attenborough theory are compared with measurements of pulses centred on 100 kHz and 1 MHz transmitted through water-saturated porous samples. The samples are 13 times larger than the original bone samples. Despite the expected effects of scattering, which is neglected in the theory, at 100 kHz the predicted and measured transmitted waveforms are similar.

Amplitude variation in calibrated audiometer systems in clinical simulations.

Manual pure tone audiometry is considered to be the gold standard for the assessment of hearing thresholds and has been in consistent use for a long period of time. An increased legislative requirement to monitor and screen workers, and an increasing amount of legislation relating to hearing loss is putting greater reliance on this as a tool. There are a number of questions regarding the degree of accuracy of pure tone audiometry when undertaken in field conditions, particularly relating to the difference in conditions between laboratory calibration and clinical or industrial screening use. This study analyzed the output sound pressure level of four different commercial audiometers, all using TDH39 headphones and each of which had recently undergone calibration at an appropriate laboratory. Levels were measured using a Bruël and Kjaer Head and Torso simulator, which accurately replicates the size and shape of a human head, including the ears. A clinical environment was simulated by a trained audiometrist replacing the headphones for each test. Tests were undertaken at three presentation levels, and at the frequencies of 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz and 6 kHz. The results showed a high level of test-retest variability, both between different audiometers and within the same audiometer. Maximum variation of sound pressure level at the ear for the same tone presentation was 21 decibels, with a particularly high level of variation at 6 kHz for all meters. An audiometer with attenuating cups exhibited significantly higher variation than ones using supral-aural headphones. Overall the variation exhibited suggests that there is a higher degree of potential error with screening pure tone audiometry than is commonly assumed and that results particularly at the 6 kHz frequency need to be assessed carefully alongside other methods such as speech audiometry.