Patent Application
20100208929
This invention relates generally to vocal microphones and, in particular, to microphones capable of rejecting undesired background noise.
Although certain cardioid or unidirectional microphones are designed to pick up sounds emanating primarily from in front of the microphone, it is fairly common that such microphones will also pick up some sounds originating from behind or to the side of the microphone. In order to reduce the amplification of these unwanted sounds, microphones may be designed to purposefully allow these sounds to enter the microphone from the rear or back of the microphone for processing by the dynamic element. Typically there is a time delay between the time the unwanted sounds enter the rear of the microphone and when the sounds enter the front of the microphone. This time delay is beneficial because there is a phase shift in the sound waves entering the front and rear of the microphone. Because of the phase shift, the sound is effectively cancelled out and not processed or amplified by the microphone.
Conventional microphones designed to removed unwanted sounds originating from the rear or side of the microphone, or reflections of desired sounds, are typically designed with a small number of ports that allow entry of some of these unwanted sounds into the rear of the microphone so that they may cancel out any such sounds entering the front of the microphone. However, due to the limited number of ports and the overall design of these conventional microphones, not all unwanted sounds in each audio frequency band are removed. Consequently, these conventional microphones tend to process and amplify some unwanted sounds.
A need exists, therefore, for an improved microphone that substantially reduces the processing and amplification of unwanted sounds. Preferably, the improved microphone would provide for an increase in front to rear signal ratio and improved side and rear cancellation.
According to one aspect of the present invention, a microphone for processing and amplification of desired acoustical signals includes an inner cylindrical housing and an outer tubular shell enclosing the inner cylindrical housing. The shell has front apertures permitting entrance of both desired acoustical signals and undesired acoustical signals, the undesired acoustical signals entering the front apertures characterized as having an acoustical frequency and a first phase. The shell also includes side apertures permitting entrance of the undesired acoustical signals at a second phase such that the undesired acoustical signals entering the side apertures are out of phase with the undesired acoustical signals entering the front apertures. The microphone also includes an annular gap between the inner cylindrical housing and the outer tubular shell such that the undesired acoustical signals entering the side apertures flow into and through the annular gap.
Preferably, the microphone includes a phasing plug assembly mounted within the top end of the cylindrical housing that includes a ring retaining a diaphragm. The desired and undesired acoustical signals entering the front apertures pass to a top side of the diaphragm, causing it to vibrate. Preferably, a magnet assembly having a resonant cavity is arranged at least partially within the interior of the ring forming a phase reversal entrance between an outside surface of the magnet assembly and an interior surface of the ring. In use, the annular gap collects the undesired acoustical signals entering the side apertures and ducts the undesired acoustical signals through the phase reversal entrance to a bottom side of the diaphragm such that the undesired acoustical signals entering the front apertures are substantially cancelled out by the undesired acoustical signals entering the side apertures.
These and other features, aspects and advantages of the invention will become more fully apparent from the following detailed description, appended claims, and accompanying drawings, wherein the drawings illustrate features in accordance with an exemplary embodiment of the present invention, and wherein:
Referring to
The microphone 10 may also include a humbucking coil 28, for example, a 60 Hz humbucking coil, and a humbucking bobbin 30 designed to shield the components inside the magnetic assembly 22 from interference from electronic equipment such as computer monitors and/or noisy lighting fixtures and controls.
A phasing plug assembly 26 is mounted above and is in acoustical communication with the magnet assembly 22. As illustrated in
As shown in
In use, unwanted sounds originating from the side or rear of the microphone 10 enter the side apertures 16 and pass through an annular gap located between the inner cylindrical housing 20 and the outer tubular shell 12 and into the phase reversal entrance 50. The phase reversal entrance 50 is in acoustical communication with the bottom of the diaphragm 34 via the sound ports 42 in the lower plate 38 so that the unwanted sound waves impact the diaphragm 34. These undesired sounds entering the side apertures 16 are out of phase with the same sound frequencies entering into the front apertures 14 of the microphone 10, therefore cancelling one another out. Thus, the front apertures 14 provide an entrance for undesired acoustical signals characterized as having an acoustical frequency and a first phase, and the side apertures 16 permit entrance of the undesired acoustical signals at a second phase such that the undesired acoustical signals entering the side apertures 16 are out of phase with the undesired acoustical signals entering the front apertures 14. The undesired acoustical signals entering the side apertures 16 flow into the annular gap between the inner cylindrical housing 20 and the outer tubular shell 12. The phase reversal entrance 50 is uniquely designed and situated to selectively regulate the entry of sound pressure wavefronts channeled up through the annular gap between the outer tubular shell 12 and the inner cylindrical housing 20.
Although certain illustrative embodiments and methods have been disclosed herein, it will be apparent from the foregoing disclosure to those skilled in the art that variations and modifications of such embodiments and methods may be made without departing from the spirit and scope of the invention. Accordingly, it is intended that the invention should be limited only to extent required by the appended claims and the rules and principals of applicable law.
