Patent Application
20160140946
The invention relates to a device and method for providing musical instrument feedback. In particular, it relates to electric guitar or bass guitar feedback, especially in situations where a guitar amplifier simulator is used or it is otherwise not convenient to achieve such feedback.
Audio feedback (also known as acoustic feedback or simply as feedback) is a special kind of positive feedback which occurs when a sound loop exists between an audio input (for example, a microphone or guitar pickup) and an audio output (for example, a loudspeaker). In the case of an electric guitar, a signal received by the guitar pickup is amplified and passed out of the loudspeaker. The sound from the loudspeaker can then be received by the pickup again, amplified further, and then passed out through the loudspeaker again. The frequency of the resulting sound is determined by resonance frequencies in the pickup, amplifier, and loudspeaker, the acoustics of the room, the directional pick-up and emission patterns of the pickup and loudspeaker, and the distance between them.
Feedback can be undesirable, particularly when it causes the loud, unpleasant “shriek” that results when the gain is too high on the output of an amplified instrument or microphone, or a microphone gets too close to a loudspeaker. Controlled feedback can, however, be desirable in some music genres because it introduces a desired distortion.
Unlike microphones, guitars and bass guitars (both acoustic and electric) can vibrate and these vibrations occur at particular frequencies. In fact, the structural vibrations of an acoustic guitar and the acoustic resonances of the guitar enclosure are coupled and serve to “color” the sound of the guitar. These harmonics are what distinguish the sound of a particular guitar.
When a microphone is used to amplify the output of an acoustic guitar, the amplified speaker closes the loop between the input and output when the radiated sound from the speaker reaches the guitar. At this point, the sound can further enhance the vibrations of the guitar. If the gain is excessive, this enhancement results in instability dubbed “feedback” by the musician. In such cases, the guitar starts vibrating excessively at a particular frequency and this vibration produces an audible tone. For guitars, this typically occurs at lower frequencies, ranging between 100 and 200 Hz, and results in a “hum.”
A similar mechanism occurs when amplifying the output of an electric guitar. Structural vibrations induced by acoustic feedback can magnify the signal generated by the sensors embedded in the guitar to “pick up” its sound, which leads to instability. Equalization can control feedback by reducing the gain at the frequency at which this problem occurs. One must take care in setting the equalization so as not to eliminate the natural harmonics of the instrument over a desired frequency range, however.
Traditionally, studio engineers who were recording electric guitars placed a microphone in front of the loudspeaker of the guitar amplifier cabinet. A similar arrangement was used for amplifying live performances in larger venues. In recent years, however, many guitarists and studio engineers are using a guitar amplifier simulator (i.e., software, also known as a virtual guitar amp) instead of miking the amplifier speaker cabinet. This technique is easier, more productive and, in many cases, better sounding. It also offers a wider range of tones not limited by the physical amplifiers available. In addition, a musician can practice wearing headphones to avoid disturbing neighbors.
Guitar amp simulators simulate many different types of amplifiers on the market, allowing a guitarist to have many choices in his guitar sound. These amp simulators also simulate different types of speaker cabinets, eliminating the need to set up a microphone to capture the sound coming from the speaker cabinet. With an amp simulator, the clean guitar sound is routed by cable directly to the recording device and monitored via headphones and/or studio monitor speakers. It is possible to achieve feedback by turning up the volume on the monitor speakers, but this is never desirable as it would be too loud in the confines of a recording studio control room where lower volumes are necessary to achieve mixing levels, i.e., individual recorded instrument and/or vocal volume levels.
Unfortunately, therefore, without a physical amplifier, the possibility of using feedback to create desirable effects is not readily available. One way to provide feedback in such cases is to first record the guitar part using the amp simulator, and then set up a speaker cabinet in another room, mike the cabinet, record any desired feedback and mix the feedback track with the original clean guitar track. This is obviously both inefficient and inconvenient, and begs the question of why not simply mike the cabinet speaker in the first place. For many engineers, the answer is that with a software guitar amp simulator, there are choices available after the guitar part is recorded. The guitar part is initially recorded “clean,” without feedback or distortion, and without the characteristics of any particular amp and/or speaker cabinet. Then, the engineer can select any virtual amp available from the software amp simulator. The producer, engineer or musician can decide to change or tweak the guitar part at any time after the clean guitar has been recorded. If, for example, they want to change just the middle part of a song, they can use the exact guitar tone they used the first time. There is no need to set up the guitar amp, speaker and microphone and adjust positions and settings to try to duplicate the exact tone they used hours, days or weeks earlier to re-create the first and only guitar part.
An object of the present invention is to provide guitar feedback in situations where it is not possible to easily achieve such feedback, as when a guitar amplifier simulator is used in lieu of a traditional amplified loudspeaker.
A further object of the invention is to provide a convenient, unobtrusive device that allows a guitarist to have a familiar natural guitar atmosphere with both amp simulator choices and feedback.
In accordance with the present invention, a method for inducing feedback in a stringed musical instrument comprises placing a vibration transducer in proximity to the strings of the instrument and energizing the transducer to produce vibrations. In a preferred embodiment, the transducer is an audio speaker.
In accordance with another aspect of the method of the present invention, the instrument is an electric guitar or bass guitar, and the method further comprises routing a portion of the audio output of the guitar to the speaker.
In accordance with yet another aspect of the invention, the method comprises passing the portion of the audio output of the guitar through a distortion circuit before routing the distorted signal to the speaker.
In accordance with still another aspect of the invention, a system for inducing feedback in a stringed musical instrument includes a vibration transducer, an attachment device for removably attaching the transducer to the instrument, and a control unit for selectively energizing the transducer to produce vibrations and thus induce feedback.
In accordance with the present invention, a vibration-producing transducer such as a small, low-volume speaker is placed against the body of an electric guitar or electric bass guitar. The speaker produces distorted guitar sounds which cause the guitar body and strings to vibrate, causing a feedback loop. As used hereinafter, the term “guitar” includes a “bass guitar.”
As shown in
Any type of transducer which produces vibrations may be used to induce vibration in the guitar body and strings. Most typically, the transducer will be an audio speaker, but a vibrating disc motor (e.g., of the type used in cell phones) or piezoelectric vibration generator may be used. Transducers other than audio speakers will produce different types of effects.
As shown in
The top surface of enclosure 14 is flat so that speaker 12 fits closely against the guitar, with the output of speaker 12 directed against the guitar and preferably with very little sound leakage. Speaker 12 may be protected by a fabric speaker grill 24 which also protects the surface of the guitar from scratching but permits sound to pass freely through. Enclosure 14 should be sized so that all or at least most of the output of speaker 12 is directed against the portion of the guitar to which housing 16 is attached. Although housing 16 is depicted as oval in shape, it may be generally cylindrical, a rectangular box or another suitable shape.
A jack (not visible in
As shown in
A distortion bypass button switch 52 is provided. When this button is depressed, the signal to speaker 12 bypasses the gain control but the tone and volume controls still function. A bypass switch 54 may be switched to determine whether both the guitar cable input and the output are mixed in distortion circuitry 32.
Control unit 30 is connected to speaker unit 10 by cable 28, which is preferably about 4 to 5 feet long and has a standard mini plug for insertion into mini jack 56. Cable 28 may alternately be hard wired to control unit 30 and/or unit 10. Alternately, a plug can be provided on one or both ends of cable 28 with corresponding jacks on control unit 30 and/or device 10 so that cable 28 can be disconnected for storage when not in use. Preferably, these plugs and jacks are stereo mini types. In yet another alternative embodiment, the audio signal from distortion circuitry 32 may be transmitted wirelessly to speaker 12, obviating the need for cable 28.
Distortion circuitry 32 may be selected to provide any desired type of distortion as is well known among musicians. Such known distortion circuits alter the audio signal from the guitar, typically by compressing the peaks of the sound wave. In a solid-state device, this is accomplished by overdriving a transistor amplifier or op amp to cause clipping. This results in numerous overtones and provides a sound that is often characterized as “warm,” “fuzzy” or “dirty.” Distortion circuitry 32 includes a small amplifier to drive speaker 12.
In an alternate embodiment, all of the components of control unit 30 may be included inside housing 16 of unit 10, resulting in a single self-contained unit. In another alternative embodiment, control unit 30 may be incorporated in a pedal of the type commonly used for creating various effects with electric guitars.
A standard guitar cable 60 is used to connect output jack 38 to the input of a guitar amplifier simulator or guitar amplifier/speaker enclosure. Preferably, a flexible “gooseneck” type guitar cable 62 is used to connect the output jack of the guitar to input jack 36 of control unit 30. This type of flexible connector holds its shape when bent and may be used to position and hold control unit 30 in a conveniently-accessible position. Of course, a standard guitar cable may also be used.
Alternately, as shown in
When the guitarist plays the guitar, sounds from the vibrating guitar strings and guitar body are captured by the guitar's pickup(s) and sent from the output jack of the guitar via cable 62 to control unit 30. There, the signal is split into two signals, one of which is input to the distortion circuit 32 and the other of which is sent via output jack 38 and cable 60 to the amp or amp simulator. The output of distortion circuit 32 is sent to speaker 12 via cable 28.
Sound generated by speaker 12 is directed against the neck or body of the guitar, causing the guitar strings to vibrate and generate feedback. The composite sound from the vibrating strings is picked up by the guitar's electronic pickup. Because speaker 12 is closely fitted against the guitar, its volume can be low and unobtrusive while still being sufficient to induce feedback. The musician can adjust the volume of the audio signal to speaker 12 using volume knob 44, and can also adjust the level of distortion from no distortion to maximum distortion using gain knob 40. Of course, knobs 40, 42, 44 and 48 could be replaced by sliders, electronic switches or other types of controls.
Alternately, a transducer may be built into a guitar when the guitar is manufactured, e.g., embedded into the material of the guitar at a suitable location. Similarly, the components of control unit 30 could also be built into the guitar.
While the invention has been described with respect to certain preferred embodiments, as will be appreciated by those skilled in the art, it is to be understood that the invention is capable of numerous changes, modifications and rearrangements and such changes, modifications and rearrangements are intended to be covered by the following claims.
