Tacoma Narrows Bridge (1940) Billah and Scanlan (1991) reported that in fact, many physics textbooks (for example Resnick et al. and Tipler et al.) wrongly explain that the cause of the failure of the Tacoma Narrows bridge was externally forced mechanical resonance. Resonance is the tendency of a system to oscillate at larger amplitudes at certain frequencies, known as the system's natural frequencies. At these frequencies, even relatively small periodic driving forces can produce large amplitude vibrations, because the system stores energy. For example, a child using a swing realizes that if the pushes are properly timed, the swing can move with a very
Amplitude panning by a pair of microphones to the amplitude difference of in-phase input signals to two loudspeakers. Assuming free field sound propagation, it has been shown that the sound field presented by these two transducers can deliver an appropriate phase difference between the positions of listener’s ears at low frequencies, where the relation between the position of phantom image and the corresponding amplitude ratio may be summarized by the so-called ‘sine law’ (similarly, the tangent law). The system was designed to work approximately below 1 kHz, above which the given phase difference becomes ambiguous, and so does the position of the