Volume 104, Issue 2, August 1998
Index of content:
- SELECTED RESEARCH ARTICLES 
104(1998); http://dx.doi.org/10.1121/1.423306View Description Hide Description
Measurements of macrosonic standing waves in gases in oscillating closed cavities are shown. The strong dependence of the pressure waveform upon cavity shape is demonstrated. This dependence is exploited to provide control of harmonic phase and amplitude, thus avoiding shocks and enabling resonant waveforms to reach macrosonic pressures. The exploitation of this dependence is referred to as resonant macrosonic synthesis (RMS). Power is delivered to the cavity by oscillating it with a linear actuator (entire resonator drive). Standing wave overpressures in excess of 340% of ambient pressure are demonstrated in RMS cavities, compared to maximum overpressures of 17% observed in cylindrical resonators. Ratios of maximum to minimum pressures of 27 were observed in RMS cavities compared to 1.3 for cylinders. Measurements are shown for four axisymmetric cavity shapes: cylinder, cone, horn-cone hybrid, and bulb. Cavities were filled with nitrogen, propane, or refrigerant R-134a (1,1,1,2-tetrafluoroethane). Physical effects which can be observed at macrosonic pressures are demonstrated. These effects include nonlinearly generated dc pressures of 40% of ambient pressure as well as hardening and softening resonance behavior for the same gas but different cavity shape. RMS, together with the entire resonator drive, provides high-power transduction of energy through resonant sound waves and opens a wide range of new commercial applications for macrosonic waves.
104(1998); http://dx.doi.org/10.1121/1.423237View Description Hide Description
The perceptual effect of modifying speech produced by deaf talkers was investigated to discover the changes necessary for disordered speech to be judged normal. Recordings of passages read by three deaf talkers were used as material. For the first two experiments, a three-syllable word was extracted from the deaf talkers’ passages and from a similar passage recorded by a hearing talker. Each of the deaf speech samples was paired with the normal speech sample to generate various continua that differed in the spectral and temporal modifications applied to them. Within each continuum, the individual stimuli varied in the shape of the spectrum envelope and were produced by linear interpolation of LPC analysis parameters between the deaf and normal speech end points. Results suggest that correcting the temporal component of deaf speech alone is not enough to make it sound normal. Spectral corrections that approximate about 70% of normal appear to be necessary for the deaf speech samples to be judged normal. A third experiment made use of a 10-syllable segment of speech in which the relative contributions of spectral and temporal adjustments were investigated. The general conclusion of these three experiments is that spectral adjustments are more important to perceptual judgments of normality than temporal adjustments.