The present invention provides a device for alternatively indicating at least a first fluid flow rate and a second fluid flow rate. The device, which may be a spirometer (e.g. a peak flow meter) comprises an aperture, a mouthpiece and a body defining a fluid flow path extending between the aperture and the mouthpiece. The body comprises a fluid flow rate indicator operable to alternatively generate at least a first sound signal and a second sound signal indicative of the first or second fluid flow rate in a first direction. The fluid flow rate indicator comprises a corrugated portion having a plurality of corrugations extending into the fluid flow path.
