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cardioid Math.|ˈkɑːdɪɔɪd|
Also -oide.
[ad. Gr. καρδιοειδής heart-shaped, f. καρδία + εἶδος form.]
A curve somewhat resembling a heart in shape.
If through a fixed point in the circumference of a circle straight lines be drawn, intersecting the circle at different points, and such that the length of each line on each side of the point of intersection is equal to the diameter of the circle, the extremities of these lines will trace out a cardioid, having its cusp at the fixed point. The cardioid is also traced out by a point in the circumference of one circle rolling round the circumference of another equal to it.
1753in Chambers Cycl. Supp., The Cardioide. 1852Salmon Higher Pl. Curve (1879) II. 44 The curve is of the form of a heart and is called the cardioide. 1879Thomson & Tait Nat. Phil. I. i. §94 We have..the case of a circle rolling externally on another of equal size. The curve in this case is called the Cardioid.
Add:[A.] 2. A cardioid microphone.
1955F. W. Alexander in J. W. Godfrey Studio Engin. for Sound Broadcasting iii. 43 When broadcasting an orchestra from an empty concert-hall..the wider acceptance angle of the cardioid is especially useful. 1961[see unidirectional a.]. 1983A. Nisbett Use of Microphones (ed. 2) 42 The original way of producing a cardioid, by combining a moving coil and a ribbon in a single case, has fallen into disuse... Most modern cardioids are even more complex.
B. adj.
1. Having the characteristic shape of a cardioid.
1922R. Keen Direction & Position Finding by Wireless ii. 38 The cardioid, heart-shape or apple diagram of reception. 1936L. S. Palmer Wireless Engin. (ed. 2) xii. 493 This heart-shaped or cardioid figure represents the polar diagram of an aerial capable of determining ‘sense’ as well as direction. 1965Wireless World Aug. 89 (Advt.), Grampian proudly present a microphone with a really good frequency response..and a genuine cardioid pick-up pattern. 1977Rolling Stone 13 Jan. 58/4 Many amateur recordists, in attempting to operate like the pros, choose directional or cardioid-pattern microphones.
2. Designating a type of microscope condenser for giving dark-ground illumination, in which the light is reflected first from the outside of a sphere and then from the inside of a surface whose cross-section is theoretically a cardioid.
1932L. C. Martin Introd. Appl. Optics II. iii. 124 Fig. 88 shows the course of the rays through a cardioid condenser as made by Zeiss. 1962W. G. Hartley Microscopy vii. 126 Zeiss formerly produced a mount for the cardioid dark-ground illuminator.
3. Of a microphone: having a cardioid pattern of sensitivity, with a maximum in a single direction.
1939Bell Lab. Rec. XVII. 339/2 The cardioid microphone can be mounted either on a floor or on a desk. 1951Microphones (B.B.C. Engin. Training Dept.) v. 65 In general, a cardioid microphone can..be used at a distance from the sound source √3 times as great as with an omni-directional microphone. 1975G. J. King Audio Handbk. ix. 205 Real cardioid microphones are costly and generally outside the pocket of the average enthusiast. |