Click here to purchase the entire book in PDF format. Wavelength Let's say that you're standing outside, whistling a perfect 1 kHz sine tone. The moment you start whistling, the first wave - the wavefront - is moving away from you at a speed of 344 m/s. This means that exactly one second after you started whistling, the wavefront is 344 m away from you. At exactly that same moment, you are starting to whistle your 1001st cycle (because you're whistling 1000 cycles per second). If we could stop time and look at the sound wave in the air at that moment, we would see the 1000 cycles that you just whistled sitting in the air taking up 344 m. Therefore you have 1000 cycles for every 344 m. Since we know this, we can calculate the length of one wave by dividing the speed of sound by the frequency - in this case, 344/1000 = 34.4 cm per wave in the air. This is known as the wavelength The wavelength (abbreviated $\lambda$) is the distance from a point on a periodic (a fancy word meaning `repeating') waveform to the next identical point. (i.e. crest to crest, or positive zero-crossing to positive zero crossing) Equation 3.8 is used to calculate the wavelength, measured in metres. $$\lambda = \frac{c}{f}$$ (4.8)