What is "pulse wave"

Pulse \Pulse\, n. [OE. pous, OF. pous, F. pouls, fr. L. pulsus (sc. venarum), the beating of the pulse, the pulse, from pellere, pulsum, to beat, strike; cf. Gr. ? to swing, shake, ? to shake. Cf. Appeal, Compel, Impel, Push.]

1. (Physiol.) The beating or throbbing of the heart or blood vessels, especially of the arteries.

   Note: In an artery the pulse is due to the expansion and contraction of the elastic walls of the artery by the action of the heart upon the column of blood in the arterial system. On the commencement of the diastole of the ventricle, the semilunar valves are closed, and the aorta recoils by its elasticity so as to force part of its contents into the vessels farther onwards. These, in turn, as they already contain a certain quantity of blood, expand, recover by an elastic recoil, and transmit the movement with diminished intensity. Thus a series of movements, gradually diminishing in intensity, pass along the arterial system (see the Note under Heart). For the sake of convenience, the radial artery at the wrist is generally chosen to detect the precise character of the pulse. The pulse rate varies with age, position, sex, stature, physical and psychical influences, etc.

2. Any measured or regular beat; any short, quick motion, regularly repeated, as of a medium in the transmission of light, sound, etc.; oscillation; vibration; pulsation; impulse; beat; movement. The measured pulse of racing oars. --Tennyson. When the ear receives any simple sound, it is struck by a single pulse of the air, which makes the eardrum and the other membranous parts vibrate according to the nature and species of the stroke. --Burke. Pulse glass, an instrument consisting to a glass tube with terminal bulbs, and containing ether or alcohol, which the heat of the hand causes to boil; -- so called from the pulsating motion of the liquid when thus warmed. Pulse wave (Physiol.), the wave of increased pressure started by the ventricular systole, radiating from the semilunar valves over the arterial system, and gradually disappearing in the smaller branches. the pulse wave travels over the arterial system at the rate of about 29.5 feet in a second. --H. N. Martin. To feel one's pulse.

   1. To ascertain, by the sense of feeling, the condition of the arterial pulse.

   2. Hence, to sound one's opinion; to try to discover one's mind.

n. 1 A kind of non-sinusoidal waveform that is similar to a square wave but lacks the perfectly symmetrical shape. 2 (context biology English) The wave of increased pressure started by the ventricular systole, radiating from the semilunar valves over the arterial system, and gradually disappearing in the smaller branches.

A pulse wave or pulse train is a kind of non-sinusoidal waveform that is similar to a square wave, but does not have the symmetrical shape associated with a perfect square wave. It is a term common to synthesizer programming, and is a typical waveform available on many synthesizers. The exact shape of the wave is determined by the duty cycle of the oscillator. In many synthesizers, the duty cycle can be modulated (sometimes called pulse-width modulation) for a more dynamic timbre. The pulse wave is also known as the rectangular wave, the periodic version of the rectangular function.

The Fourier series expansion for a rectangular pulse wave with period and pulse time is

$$f(t) = \frac{\tau}{T} + \sum_{n=1}^{\infty} \frac{2}{n\pi} \sin\left(\frac{\pi n\tau}{T}\right) \cos\left(\frac{2\pi n}{T} t\right)$$

Note that, for symmetry, the starting time in this expansion is halfway through the first pulse. The phase can be offset to match the accompanying graph by replacing with .

A pulse wave can be created by subtracting a sawtooth wave from a phase-shifted version of itself. If the sawtooth waves are bandlimited, the resulting pulse wave is bandlimited, too. Another way to create one is with a single ramp wave (sawtooth or triangle) and a comparator, with the ramp wave on one input, and a variable DC threshold on the other. The result will be a precisely controlled pulse width, but it will not be bandlimited.

Acoustically, the rectangular wave has been described as having a more "narrow and nasal" sound than a perfect square wave, and its characteristic sound features prominently in many Steve Winwood songs.