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Hearing Aids
Published in Nick Zacharov, Sensory Evaluation of Sound, 2018
Lars Bramsløw, Søren Vase Legarth
When using the above-mentioned open fittings and a digital hearing aid, another acoustic artefact is introduced: The comb filter effect. In the ear, the direct sound is added to the amplified and delayed sound causing phase. Adding a direct and a delayed signal leads to a very rippled frequency response with notches spaced at 1/ΔT, where ΔT is the processing delay. For equal levels and a frequency-independent delay of ΔT there will be destructive interference (–∞ dB) for all multiples of the corresponding frequencies (2N + 1) / (2 * ΔT) and constructive interference (+ 6 dB) for frequencies N / ΔT. The result is a ‘tube’ sound, similar to that of listening through a tube or pipe, caused by mid-range resonance (see (Section 9.12 for more details on comb filtering).
Project 1: Guitar Special Effects
Published in Thad B. Welch, Cameron H.G. Wright, Michael G. Morrow, ® to C with the TMS320C6x DSPs, 2016
Thad B. Welch, Cameron H.G. Wright, Michael G. Morrow
Fuzz is an intentionally introduced distortion in the signal, typically caused by “clipping” or limiting the amplitude variations of the signal (see Figure 10.17 for a simple example). This effect was first discovered accidentally when the dynamic range of a tube-based amplifier stage was exceeded, which caused clipping, which in turn resulted in higher-frequency harmonics (harmonic distortion) being added to the original signal. Heated debates continue today about the “tube” sound of fuzz versus the “solid-state” or “transistor” sound of fuzz. Keep in mind that Figure 10.17 is a very simplistic example of clipping. The signal can be clipped so that the positive portion is limited to a different magnitude than the negative portion, or the clipping can be gradual rather than “flat.” These variations (and others) will all produce a different sound of fuzz effect. Furthermore, the clipping is often followed by a frequency selective filter (lowpass or bandpass are the most common) to adjust the “harshness” or “color” of the fuzz sound. More sophisticated fuzz effects also have the option to engage a frequency selective filter before the clipping stage, in order to clip just a certain band of frequencies, then add this back to the unmodified or fully clipped signal. The possibilities are endless; experiment for the sound you like!
Boiling heat transfer and CHF for subcooled water flowing in a narrow channel due to power transients
Published in Experimental Heat Transfer, 2020
M. Shibahara, Q.S. Liu, K. Hata, K. Fukuda
Figure 1 illustrates a schematic of the experimental setup, which consisted of a canned-type pump, preheater, Coriolis mass flowmeter, test section installed inside of the platinum tube, sound level meter, an expansion tank connected to a pressurizer, and a cooler. In the test section, the platinum tube that acted as a heater was oriented vertically and connected to two copper electrodes. A Bakelite plate between the copper electrodes was bounded for electrical insulation. The inner diameter of the tube was 1.0 mm, and the heated length was 40.9 mm. The boiling initiation (BI) was measured by the sound level meter.