GB506668A - Improvements in and relating to microphones - Google Patents

Abstract

506,668. Microphones. ALEXANDER; F. W:, and SHORTER, D. E. L. Dec. 1, 1937, No. 33275. [Class 40 (iv)] Microphone appar. atus comprises a velocity microphone, spacing means adapted tc rest against the face of a user whereby the vibratory part of the microphone can be located at a fixed mininum distance from the mouth, this distance being sub. stantially less than 18 inches, and a baffle for preventing impulsive draughts from passing directly from the mouth of the user to the vibratory part but allowing sounds from the mouth tc pass around the edges of the baffle to the said vibratory part, and attenuating means which may be acous. tical and/or electrical and which substantially compensate for the discrimination of the microphone in favour of the lower frequencies of the sound from the speaker. As shown, a ribbon microphone is suspended by rubber bands 2 in a cubical casing 4 of perforated metal lined with silk or other fabric and having a perforated metal cover 11 lined with wire gauze 10. A ring 12 mounted on the cover by rods 9 facilitates the use of the microphone with the ribbon at the correct distance from the mouth. The ribbon 13 is mounted between the polepieces of a U-shaped magnet 14, the limbs of which are formed with U-shaped slots. Perforated metal strips 21 lined with silk are located in front of and behind the ribbon to attenuate the lower frequencies. The ends of the ribbon are connected by leads 17 to the primary winding of a transformer 7 which is designed to favour the higher frequencies. The leads 17 pass through a pad 18 of cotton wool and the output conductors are supported in a cable grip 20 disposed in the handle 6. The microphone is mounted in its casing so that the body of the magnet is interposed between the source of sound and the ribbon 13 to act as the baffle against impulsive draughts from the user.