The object on the right-hand side of Fig. 1 is the whistling mechanism of an old-fashioned tea kettle. This started me thinking about similar devices in which a thin blade of air strikes a sharp wedge and a resonator is used to pick out specific frequencies. This note tells how I went about using the frequency spectrum application on a smartphone…

I have been tinkering with ultrasonic transducers once more. In earlier notes I reported on optics-like experiments performed with ultrasonics, described a number of ultrasonic interferometers, and showed how ultrasonic transducers can be used for Fourier analysis. This time I became interested in trying the technique of using two detectors in…

Presents experiments that use Helmholtz resonators and have been designed for a sophomore-level course in oscillations and waves. Discusses the theory of the Helmholtz resonator and resonance curves. (JRH)

Describes an experiment that uses the ultrasonic transducer for demonstrating the Fourier components of waveshapes such as the square and triangular waves produced by laboratory function generators. (JRH)

Describes demonstrations used by the nineteenth century physicists to determine if two bodies oscillating at the same acoustic frequency were in phase. (GA)

Discusses theory of the rotating mirror, its use in measuring the velocity of the electrical signal in wires, and the velocity of light. Concludes with a description of the manometric flame apparatus developed for analyzing sound waves. (SK)