Watt (W): the unit of power; the power dissipated when one joule of energy is expended in one second.

Wave: in an elastic medium; a mechanism whereby a disturbance, and the energy associated with it, is propagated through an elastic medium; the disturbance results in vibrations of the particles of the medium, vibrations transmitted to nearby regions as a result of the elastic and inertial nature of the medium, resulting in a disturbance which is a function of both position and time.

Waveform: a graph showing how a variable at one point in a wave (e.g. sound pressure or particle velocity) or vibration varies with time.

Wavefront: the leading edge of a progressive wave, along which, the vibration of the particles of the medium are in phase.

Wavelenght: the minimum distance between two points that are in phase within a medium transmitting a progressive wave.

Weber-Fechner law: a law of psychology, which states that the change of subjective response to a physical stimulus is proportional to the logarithm of the stimulus.

Weighted sound reduction index, Rw: a single figure value of sound reduction index, derived according to procedures given in BS EN ISO 717-1, used for rating and comparing partitions and based on the values of sound reduction index at different frequencies.

Weighted standardized impact sound pressure level, L’nT,w: a single-figure value of impact sound insulation performance, derived according to procedures in BS EN ISO 717-2, used for comparing and rating floors and based in the values of L’nT at different frequencies; values of L’nT,w are specified in the Building Regulations.

Weighted standardized level difference, DnT,w: a single-figure value of airborne sound insulation performance, derived according to procedures given in BS EN ISO 717-1, used for rating and comparing partitions based on the values of D at different frequencies; sound insulation performance requirements in the Building Regulations are specified in terms of values of DnT,w + Ctr.

Weighting: see under frequency weighting and time weighting.

White finger: see under vibration white finger.

White noise: a random broadband noise which contains equal power per unit bandwidth, so it has a flat, i.e. horizontal, frequency spectrum when plotted on a linear frequency scale (cf. pink noise).

Whole-body vibration: vibration transmitted to the body as a whole.