The vocal tract is a resonator, and the transmission of a sound through an acoustic resonator is highly dependent upon frequency. Sounds at the resonance frequency are less attenuated than other sounds, and are therefore radiated with a higher relative amplitude, or with a greater relative loudness than other sounds. The vocal tract has four or five important resonances called formants. Each formant is associated with a standing wave, that is, with a static pattern of pressure oscillations whose amplitude is at a maximum at the glottal end and near a minimum at the lip opening. The lowest formant corresponds to a quarter of a wavelength, which is to say that a quarter of its wavelength fits within the vocal tract. Similarly, the second, third and fourth formants correspond respectively to a three-quarters wavelength, one and a quarter wavelengths and one and three-quarters wavelengths. Which of the following is not a formant wavelength?
A. 3A/4.
B. A/4.