The present relates to microphone assemblies such as lectern microphones handheld microphones and other microphones used in pickup of voice sounds for amplification and broadcast to an audience.
Typically the prior art microphones require a speaker to be a set distance close to the microphone. For example if a microphone and audio broadcast system is set to sound good when the speaker's lips are three inches in front of the microphone, then the speech volume heard by the audience will probably weaken when the speaker moves back from microphone.
When the lips of the speaker get very close to the microphone, a different problem occurs in that bass tones appear amplified substantially more than higher tones in the output of the microphone transducer. This is known as the proximity effect. While the proximity effect may enrich the bass tones of a singer, the proximity effect often deteriorates normal speech quality heard by audiences in churches, board rooms or lecture halls.
Often a plurality of microphones are employed in a public audio broadcast system. As the number of open microphones increases, the likelihood of undesirable feedback amplification increases. Prior art systems sometimes include mixers or gates, known as noise gates, that can be programmed to automatically attenuate or mute all microphones except for one microphone picking up speech. The noise gates are not always reliable. For example, the sound of a choir in a church can produce enough background noise to open the gate of a microphone at the wrong time.
One prior art alternative to the sound activated gating of microphone inputs is the employment of proximity sensors, such as infrared or ultrasonic sensors, detecting the presence or absence of a person adjacent the microphone to open or close the microphone. These prior art sensors have been built into the microphone housing or attached to a lectern to operate gates opening or closing the signal lines to the microphone. Incorporating sensors into the microphone housing is expensive and risks compromising the microphone acoustics as well as causing undesirable signal induction. Sensors mounted on a lectern can be covered by papers, books or other objects on the lectern preventing proper operation of the microphone.
Amplification systems which receive the outputs of the microphones and drive speakers broadcasting sound to audiences often include advanced audio processors which can be programmed to improve the quality of the audio broadcast to an audience. For example, automatic gain control (AGC) can be employed to maintain the level of sound broadcast to the audience. However these systems are often expensive, difficult to wire and program, and occupy a cabinet or rack requiring significant space in a room.
The present invention contemplates a compact package or device which can be incorporated in the line from a microphone. In one embodiment the device is a unit having connectors at opposite ends for simply being plugged in series between the connector on a microphone and its mating connector on a lectern or cable. Alternatively the device can be connected or wired into the line within a lectern or anywhere prior to connection to the amplification system.
In a first aspect the present invention is summarized in a microphone enhancing device for incorporation in a line from a transducer which converts audio sound into an electric signal wherein the device includes means for dividing the electric signal into a low band signal and a high band signal. A signal processor detects a signal level above a threshold level and in response reduces the magnitude of the low band signal irrespective of any reduction in the magnitude of the high band signal. A mixer recombines the reduced low band signal and the high band signal to produce a microphone output signal. It is discovered that this reduction of the level of bass tones reduces the proximity effect improving the quality of speech broadcast to an audience.
When electronics such as signal processors are employed in the microphone enhancing device, the device can easily include automatic gain control for the electric signal when the electric signal is below the threshold.
In a second aspect the present invention is summarized in a microphone enhancing device on which is mounted a flexible gooseneck supporting an infrared sensor on its distal end. The microphone enhancing device can be incorporated in a line from an audio transducer supported by another flexible gooseneck on a support. In the absence of detection of the presence of a person adjacent the microphone, the electric audio signal is muted or attenuated by the microphone enhancing device. Having the infrared sensor mounted on a separate gooseneck provides improved sensing of a person adjacent the microphone along with reducing the chance of the infrared sensor being covered by papers on a lectern. Additionally the mounting of the infrared sensor on a gooseneck enables the infrared sensor to be positioned to receive infrared from different directions.
In a third aspect of the invention, a microphone enhancing device incorporates connectors on opposite ends of an elongated housing for being plugged between a microphone and a cable. An infrared sensor is mounted on a third connector which mates with a fourth connector in the housing so that the infrared sensor can be plugged and unplugged to the device. Circuitry within the device mutes signals from the microphone when the signals from the sensor indicate the absence of a person adjacent the microphone.
Other objects, advantages and features of the invention will be apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings
As shown in
Referring to
In the variation of the microphone system shown in
In a still further variation (not shown) of the microphone system, the device 20 can be made without connectors for being wired directly into the microphone lines within a lectern and for being wired to a phone jack (not shown) mounted in the lectern for receiving the infrared sensor plug 42.
The circuitry in the device 20 is shown in
A cover 86,
Referring to
When step 104 is false the program proceeds to step 110 where it is determined if the AGC/proximity effect button 80 is depressed. If true the program in procedure 112 changes an enable/disable status or limits for automatic gain control and proximity effect correction. Initially the limits are set at zero for no automatic gain control and no proximity correction. A first depression of button 80 sets the automatic gain limit to +6 dB and the proximity effect limit to −12 dB, and a second depression sets the automatic gain limit to +9 dB and leaves the proximity effect limit at −12 dB. A third depression of button 80 returns the limits to zero to disable automatic gain control and proximity effect correction. The number of selectable limits for automatic gain control and/or for proximity correction can be increased to thus increase the number of depressions required to step through the possible selections and back to zero. From the procedure 112, the program cycles back to step 104 through step 108.
When both steps 104 and 110 are false, the program in step 114 determines if the sensing button 82 is depressed. If true, procedure 116 sets a sensitivity level for detecting presence of a person adjacent the microphone. A first depression selects a first sensitivity, a second depression selects a second sensitivity, and a third depression returns the sensitivity to zero to disable the detection of the presence of a person. Additional sensitivities may be programmed to increase the number of depressions required to step through the range of sensitivities and back to zero. With infrared sensing enabled (one of the sensitivities selected), step 108 is true and branches to step 118 which determines whether or not the infrared radiation impinging on the sensor 26 indicates a person is adjacent the microphone based upon the sensitivity selected in procedure 116. If true, step 118 branches to procedure 120 where muting of the audio signal is turned off, and if false, step 118 branches to procedure 122 where the audio signal is muted by having the digital signal processors 68 and 70 attenuate or eliminate the audio signals. The ability to select different sensitivities enables microphone gating to be set for speakers at different distances from the microphone; in some circumstances it may be desirable to set gating at a relatively close position while in other circumstances the gating can be set to occur at a relatively far distance.
With neither of the buttons 80 and 82 depressed, the program proceeds to step 126 where it is determined if AGC/proximity effect correction is enabled. If true the program branches to step 128 where it is determined if the present absolute average audio level is above the previously determined threshold level. If true, the program in procedure 130 causes the digital signal processor 70 to attenuate the lower frequency band proportionally to the amount that the present average audio level exceeds the threshold level up to limit (−12 dB) set by the procedure 112. It is noted that the attenuation of the low frequency band is performed without any attenuation or irrespective or any attenuation of the high frequency band; the high frequency band can be attenuated by a small amount to keep the present absolute average audio level close to the threshold. It is found that this attenuation of the low frequency band irrespective of attenuation of the high frequency band reduces the proximity effect (the bass tones appearing to be amplified substantially more than the higher tones) when the speaker's lips are very close to the microphone.
When the present absolute average audio level is below the threshold level, step 132 branches to procedure 134 where the audio levels of both the low level and high level bands are increased proportionally to the amount that the absolute average audio level is below the threshold level. The amount of gain or increase is limited by the limit selected in procedure 112 (+6 dB or +9 dB). Thus when the speaker moves back from the microphone and the audio pickup level by the microphone is reduced, the audio output from the enhancement device 20 will tend to reduce or eliminate any drop off in the sound level broadcast to an audience.
The microphone enhancing device 20 combines an automatic gain control, a band-limited compressor, and a gate in one very compact package that is small enough and efficient enough to plug into the base of almost any microphone. It uses very low current components, so that it can be powered with the phantom power that is normally delivered to a microphone from its mixer. This module 20 replaces a large unit with processors in a rack. Since the device 20 does not need a power supply, large case, a complicated user interface, or extensive processing power, an amplification system employing one or more of the devices 20 in series with microphones can be relatively inexpensive. It can be used in churches, lecture halls, and conference rooms eliminating the need of a sound controller to adjust audio levels and gate microphones.
It is intended that the above detailed description of the invention and the accompanying drawings be interpreted as being only illustrative of one or more preferred embodiments and that many modifications, variations and changes in detail can be made to the described embodiments without departing from the scope and spirit of the invention. For example, the described structure has two pushbutton switches, a specific crossover frequency, an absolute average audio level, a −12 dB attenuation limit, and +6 dB and +9 dB automatic gain limits; however three or more switches, other crossover frequencies, measured audio levels, attenuation limits and gain limits can be used and may in some circumstances be found to be better.