Loudness discomfort levels (LDLs) were measured in dB HL and SPL at discrete frequencies between 500 to 4000 Hz on 31 hearing-impaired ears using TDH-50P and ER-3A earphones. The results revealed no significant differences in the measured sound pressure level (SPL) between the two earphones at all test frequencies. However, with dB HL measurements, statistically significant differences were rev...

True distance memory-based heuristics (TDHs) were recently introduced as a way to obtain admissible heuristics for explicit state spaces. In this paper, we introduce a new TDH, the portal-based heuristic. The domain is partitioned into regions and portals between regions are identified. True distances between all pairs of portals are stored and used to obtain admissible heuristics throughout th...

Noise-excluding earphones may be subdivided into circumaural earphones and noise-attenuating earphone enclosures. Two versions of 'Otocups', an example of the latter subdivision, were evaluated in a series of experiments and in comparison with a conventional type of earphone (Telephonics TDH-39 receiver in a MX-4I /AR cushion). The experiments involved a comparison of auditory threshold, artifi...

In November 1988, a physician in west Texas reported three cases of silicosis in sandblasters to the Ector County Health Department (ECHD). One of the workers, a 34-year-old man, subsequently died with acute silicotic alveolar proteinosis. All three workers had been employed at a facility that sandblasted oil-field drilling pipes. Following the physician's report, in January 1989, the ECHD and ...

This paper presents an optimization of the electric power quality by designing a 9 steps multilevel power inverter, which adopts a multi-PWM optimized using genetic algorithms (GA), and minimizing Total Harmonic Distortion (THD) of the first 50 harmonics to about 0%. This optimization is considered an alternative technique because it reduces the expression used to quantify TDH numerically. Part...