Co-Occurrence of Hypernasality and Voice Impairment in Amyotrophic Lateral Sclerosis: Acoustic Quantification

Purpose Hypernasality and atypical voice characteristics are common features of dysarthric speech due to amyotrophic lateral sclerosis (ALS). Existing acoustic measures have been developed to primarily target either hypernasality or voice impairment, and the effects of co-occurring hypernasality-voice problems on these measures are unknown. This report explores (a) the extent to which acoustic measures are affected by concurrent perceptually identified hypernasality and voice impairment due to ALS and (b) candidate acoustic measures of early indicators of hypernasality and voice impairment in the presence of multisystem involvement in individuals with ALS. Method Two expert listeners rated severity of hypernasality and voice impairment in sentences produced by individuals with ALS ( n = 27). The samples were stratified based on perceptual ratings: voice/hypernasality asymptomatic, predominantly hypernasal, predominantly voice impairment, and mixed (co-occurring hypernasality and voice impairment). Groups were compared using established acoustic measures of hypernasality (one-third octave analysis) and voice (cepstral/spectral analysis) impairment. Results The one-third octave analysis differentiated all groups; the cepstral peak prominence differentiated all groups except asymptomatic versus mixed, whereas the low-to-high spectral ratio did not differ among groups. Additionally, one-third octave analyses demonstrated promising speech diagnostic potential. Conclusions The results highlight the need to consider the validity of measures in the context of multisubsystem involvement. Our preliminary findings further suggest that the one-third octave analysis may be an optimal approach to quantify hypernasality and voice abnormalities in the presence of multisystem speech impairment. Future evaluation of the diagnostic accuracy of the one-third octave analysis is warranted.

Development of a Linear Acoustic Array for Aero-Acoustic Quantification of Camber-Bladed Vertical Axis Wind Turbine

Vertical axis wind turbines (VAWT) are a source of renewable energy and are used for both industrial and domestic purposes. The study of noise characteristics of a VAWT is an important performance parameter for the turbine. This study focuses on the development of a linear microphone array and measuring acoustic signals on a cambered five-bladed 45 W VAWT in an anechoic chamber at different tip speed ratios. The sound pressure level spectrum of VAWT shows that tonal noises such as blade passing frequencies dominate at lower frequencies whereas broadband noise corresponds to all audible ranges of frequencies. This study shows that the major portion of noise from the source is dominated by aerodynamic noises generated due to vortex generation and trailing edge serrations. The research also predicts that dynamic stall is evident in the lower Tip speed ratio (TSR) region making smaller TSR values unsuitable for a quiet VAWT. This paper compares the results of linear aeroacoustic array with a 128-MEMS acoustic camera with higher resolution. The study depicts a 3 dB margin between two systems at lower TSR values. The research approves the usage of the 8 mic linear array for small radius rotary machinery considering the results comparison with a NORSONIC camera and its resolution. These observations serve as a basis for noise reduction and blade optimization techniques.

Deep-water calibration of echosounders used for biomass surveys and species identification

Acoustic quantification of aquatic biomass using echosounders requires accurate calibration. With the advancing applications of deep-water echosounders involving moored, towed, profiling and autonomous instruments, calibration of echosounders at the operating depth is needed to ensure unbiased estimates of biomass and species identification. In this context, the deepwater calibration acoustic facility (DeCAF) was used to examine the depth-dependent variations in on-axis gain (G0) and equivalent two-way beam angle (Ψ) of three different transducers, operating at 38 (Simrad ES38-DD and MSI-38) and 120 kHz (Simrad ES120-7CD) used for biomass surveys and species identification. The analyses carried out using the sphere calibration method reveal significant variations in calibrated G0 and Ψ that in combination could result in substantial systemic biases in quantitative biomass estimation and species identification. The depth-dependent G0 variations derived using the DeCAF system are in accordance with available deep-water calibration results, demonstrating reasonable repeatability of target strength measurements (±0.6 dB) over the calibration deployments. Importantly, Ψ of the transducers was calculated to be consistently lower than the values specified by the manufacturer, and for one transducer would result in 18% change in the estimated biomass. These results highlight the potential for bias if the Ψ of transducer is not independently calculated using the actual survey echosounder.

Efficient and Noise Reduced Design of Axial Fans Considering Psychoacoustic Evaluation Criteria

Axial fans are the largest group of blowers and thus have a significant impact on their environment: Their demand for electrical power and the generation of a significant noise emission, have a negative impact on the environment.In this work the improvement of efficiency and reduction of noise emission are subject of the investigations. Several types of low-pressure axial fans are subject of this investigation. Measurements of pressure rise, efficiency and acoustic behavior will be presented for different blade geometries. The modifications of forward- and backward-skewed blades are compared to a unskewed blade geometry. The forward-skewed configurations show an improvement on the hydraulic properties, the efficiency and reduce the noise emission whilst the backward-skewed configurations improve the acoustic behavior at low flow rates with flow detachment occurring. Besides an acoustic quantification of the noise emission using the sound power level, psychoacoustic methods like loudness and sharpness were used.