Abstract:
Methods, systems and apparatus are described for mitigating noise during sound recording. A noise mitigating microphone attachment comprises a foam structure. A first cavity extending from a first opening at a surface of the foam structure and into the foam structure. A microphone is inserted into the first cavity with sound receiving elements of the microphone fully installed in the structure. A second cavity extending from a second opening at the surface of the foam structure and into the foam structure is configured to receive sound from a sound source. The first cavity is fluidly connected to the second cavity within the foam structure so that a junction is formed between the first cavity and the second cavity. The junction, the sound cavity, and the sealing of the microphone work to shield the sound receiving elements of the microphone from sound other than received through the second opening.

Description:
BACKGROUND 
     When a microphone is used to record a performance in a space that has not been treated for sound recording, sound that is unrelated to the performance may be picked up by the microphone. Ambient noise or “room tone” can include noise originating within the space, such as the sound of an air conditioner or computer fan in the room. Noise entering the space from the exterior, such as traffic noise may also contribute to ambient noise levels. Ambient noise that is picked up by a microphone during the recording of a performance can detract from the quality of the recording. 
     Additionally, performance sound can be reflected from interior surfaces of the space, such as walls, ceiling, floor, furniture, etc. When the reflected sound waves arrive at the microphone, the reflected sound waves may be out of phase with the sound waves traveling directly from the performer to the microphone. These reflected sound waves may be picked up by the microphone as a muddled version or echo of the performance. 
     Because of these issues, performances are often recorded in a room that is specially treated for sound recording. For example, the interior surfaces of the room may be treated with sound absorbing materials to reduce reflections of performance sound within the room. The windows and doors of the room may be reinforced or constructed from materials designed to reduce the intrusion of exterior noise into the space. Additional measures may be taken to reduce machine noise in the room. Such measures can make treating a room for sound recording a costly and complicated endeavor. Moreover, when sound recording occurs within a home, it may be undesirable to alter the appearance of the room as needed to accommodate sound recording. 
     Portable sound recording booths may be set up within a room that is not treated for sound recording. The portable sound recording booth may have walls and a ceiling treated with sound absorbing material to reduce the amount of reflected sound picked up by a microphone. The booth may be costly, require a complicated assembly process and, when assembled, can occupy a substantial amount of space within a room. 
     Embodiments of the invention solve these and other problems. 
     BRIEF SUMMARY 
     Methods and apparatus are described for mitigating noise with a portable microphone attachment. 
     According to one embodiment, an attachment for a microphone comprises a foam structure. A first cavity extending from a first opening at a surface of the foam structure and into the foam structure is configured to seal a microphone at least partly into the cavity with sound receiving elements of the microphone fully installed in the structure. A second cavity extending from a second opening at the surface of the foam structure and into the foam structure is configured to receive sound from a sound source. The first cavity is fluidly connected to the second cavity within the foam structure so that a junction is formed between the first cavity and the second cavity. The junction, the sound cavity, and the sealing of the microphone work to shield the sound receiving elements of the microphone from sound other than received through the second opening. 
     In another embodiment, a system for noise mitigation comprises a microphone and a means for installing the microphone within a structure such that sound receiving elements of the microphone are at least partially sealed within the structure. A cavity extends from an opening at the surface of the structure to a second position within the structure such that an airspace is located between the second position and the sound receiving elements when the microphone is held by the means for installing. 
     In a further embodiment, a method for mitigating noise comprises receiving a microphone through a first opening of a foam structure into a first cavity in the foam structure. The microphone extends through the first cavity into a second cavity in the foam structure. The second cavity is fluidly connected to the first cavity within the foam structure and extends from a second opening at a surface of the foam structure. Performance sound is received from a performance sound source via the second cavity. Sound waves incident on an exterior surface of the second cavity are attenuated by the foam structure. 
     To better understand the nature and advantages of the present invention, reference should be made to the following description and the accompanying figures. It is to be understood, however, that each of the figures is provided for the purpose of illustration only and is not intended as a definition of the limits of the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an illustrative noise mitigating microphone attachment, according to an embodiment. 
         FIG. 2  shows an illustrative pop filter, according to an embodiment. 
         FIG. 3  illustrates the insertion of a pop filter and a microphone into an illustrative noise mitigating microphone attachment, according to an embodiment. 
         FIG. 4  is a front view of an illustrative noise mitigating microphone attachment shown seated in a shock mount, according to an embodiment. 
         FIG. 5  is an illustrative flowchart of a process for mitigating noise during a recording with a noise mitigating microphone attachment, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention relate to mitigating noise during a sound recording with a noise mitigating microphone attachment. Noise can refer to any unwanted sound, i.e., sound that is not desirable to have a microphone detect during a recording. For example, it may be desirable that noise such as ambient noise and reflections of sound waves originating from a performance sound source is mitigated. The noise mitigating microphone attachment can reduce the amount of noise that a microphone will pick up during a sound recording. 
     The noise mitigating microphone attachment is typically a foam structure, such as a foam sphere. The noise mitigating microphone attachment can have two openings. A microphone can be inserted through one of the openings into a first hollow cavity (“microphone cavity”) within the foam structure. The second opening may be placed proximate to a sound source, such as a vocalist or an instrument. Sound radiating from the sound source travels through the second opening into a second hollow cavity (“sound cavity”). The microphone cavity and the sound cavity can intersect, allowing sound from the sound source to travel to the microphone via the sound cavity. In some embodiments, the microphone can extend through the microphone cavity into the sound cavity. 
     The microphone can be attached to the foam structure by an elastic coupling between the microphone and the foam structure. The elastic coupling may form a seal around the casing of microphone. The seal can reduce the amount of noise that enters the sound cavity through the microphone cavity. 
     The structure (e.g., foam) surrounding the sound cavity can be a sound attenuating material for attenuating sound waves incident on the exterior surface of the sound cavity, such that sound waves traveling through the structure into the sound cavity are attenuated. In some embodiments, the structure can absorb sound incident on the exterior surface of the noise mitigating microphone attachment. The structure may additionally attenuate sound waves incident on the interior surface of the sound cavity, such that sound waves traveling through the structure from the sound cavity to the exterior of the structure are attenuated. The structure can further absorb noise incident on the interior surface of the sound cavity. Performance sound received at the opening into the sound cavity can be channeled along the sound cavity to the microphone. 
       FIG. 1  shows a side view of a noise mitigating microphone attachment according to an embodiment. Noise mitigating microphone attachment  100  can include structure  102  having a sound cavity  104  and a microphone cavity  108 . In some embodiments, structure  102  is a foam having sound absorbing properties. For example, structure  102  may be polyurethane foam, such as an open cell polyurethane foam. The foam may have an Indentation Force Deflection (IFD) at 25% deflection between 40 and 150 pounds per 50 square inches (lb./50 in. 2 ) , such as 65 to 70 lb./50 in. 2 , e.g., 70 lb./50 in. 2 . The foam may have a density threshold between 1.5 and 3.5 pounds per cubic foot (PCF), such as 2.45-2.65 PCF, e.g., 2.5 PCF. Polyurethane foam may be fabricated in a mold. The foam can be fabricated with an integral skin or may be fabricated or modified to have no integral skin. 
     Structure  102  may have a spherical shape. The spherical shape can allow the noise mitigating microphone attachment to be supported within a shock mount, as described further below. Polyurethane foam may experience discoloration over time, and such discoloration may be relatively inconspicuous on a form having a spherical shape (compared with other shapes) due to even exposure of the sphere&#39;s surface to air. Structure  102  may be a sphere having a diameter in the range of 12 inches to 36 inches, such as 20 inches to 30 inches, e.g. 23-½″ inches. The spherical shape may also facilitate seating of the noise mitigating microphone attachment within a shock mount. This allows the noise mitigating microphone attachment to be used with a microphone mounted to a microphone stand with a shock mount. 
     Sound cavity  104  may extend from an opening  106  at the surface of structure  102 . In some embodiments, sound cavity  104  has a cylindrical shape. A cylindrical shape can allow even absorption and/or reflection of sound around the circumference and along the interior of sound cavity  104 . It will be understood that due to sound absorbing characteristics of the material of which structure  102  may be composed, reflection of sound occurring within sound cavity  104  may be low or negligible. Sound cavity  104  may have a diameter in the range of 1 inch to 8 inches, such as 4 inches to 5 inches, e.g. 4-¼ inches. Sound cavity  104  may have a length in the range of 3 inches to 12 inches, such as 5 inches to 6 inches, e.g. 5-½ inches. The distance from sound cavity  104  to the outer surface of structure  102  may be in the range of 1 inch to 6 inches, such as 1-½″ to 3 inches, e.g., 2 inches. 
     Microphone cavity  108  may extend from an opening  110  at the surface of structure  102  and may intersect sound cavity  104 . In some embodiments, microphone cavity  108  has a cylindrical shape. A cylindrical shape can allow microphone cavity  108  to accommodate microphones having a variety of casings, such as cylindrical casings, rectangular casings, etc. A microphone may be inserted into microphone cavity  108  via opening  110 . The microphone may extend through microphone cavity  108  into sound cavity  104 . Microphone cavity  108  may have a diameter in the range of ½ inch to 3 inches, such as 1 inch to 2 inches, e.g. 1-¾ inches. Microphone cavity  108  may have a length in the range of 1 inch to 6 inches, such as 1-½ inches to 3 inches, e.g. 2 inches. 
     The microphone can be located at a distance from opening  106 , such a distance in a range of 1 inch to 8 inches, such as 1-½ inches to 4 inches e.g., 2-1/2 inches. The microphone can also be located at a distance from the end of sound cavity opposing opening  106 , such as a distance in a range of 1 inch to 8 inches, such as 2 to 5 inches, e.g., 3 inches. Locating the microphone at a distance from opening  106  allows noise entering sound cavity  104  to interact with absorptive interior surface of sound cavity  104  before arriving at a microphone in microphone cavity  108 . For example, the noise may enter sound cavity at an angle such that it is absorbed by the interior surface of sound cavity  104 . Sound cavity  104  may have a minimal effect on performance sound travelling directly from the performance sound source to the microphone. 
     Sound cavity  104  and microphone cavity  108  may be oriented at a variety of angles with respect to one another. For example, the longitudinal axis of sound cavity  104  and the longitudinal axis of microphone cavity  108  may be perpendicular with respect to one another, as shown in the illustrative example of  FIG. 1 . In other embodiments, the longitudinal axis of sound cavity  104  may be aligned with the longitudinal axis of microphone cavity  108  (e.g., a single cavity extending through the noise mitigating microphone attachment can function as both microphone cavity and sound cavity, receiving a microphone at one end of the cavity and receiving sound at the other end of the cavity.) 
     A performance sound source may be placed proximate to opening  106  of sound cavity  104 . For example, microphone attachment  100  may be positioned such that opening  106  is aligned with and facing the mouth of a vocalist. In another example,  106  may be positioned adjacent to an instrument. Typically, opening  106  would be placed at a location relative to the performance sound source similar to where a microphone would be placed for recording the performance sound source. A microphone having no noise mitigating microphone attachment may be placed at a distance from a performance sound source to protect the performance sound source from damage due to contact with instruments, being knocked over, etc. Opening  106  of noise mitigating microphone attachment can be placed closer to a performance sound source than a microphone would be placed due to the protection against impact resistance that a noise mitigating microphone attachment provides to a microphone. 
       FIG. 2  shows a pop filter  200  that can be coupled to a noise mitigating microphone attachment, according to an embodiment. For example, pop filter  200  can be inserted into opening  106  of attachment of noise mitigating microphone attachment  100 . A pop filter can be used to reduce and/or eliminate popping sounds caused when plosive sounds (such as sound that may occur when the letter “B” or “P” is pronounced) and sibilants (such as sound that may occur when the letter “S” or “Z” is pronounced) are recorded by a microphone. Pop filter  200  can include base  206  and lip  204 . Base  206  and lip  204  can be metal, plastic, or other material. Base  206  and lip  204  can be fabricated as a single part. Lip  204  may extend beyond opening  106  over the surface of structure  102 . Pop filter  200  can include mesh  202  extending across the area defined by the interior circumference of lip  204 . Mesh  202  may be, e.g., a polyester, metal, or nylon mesh. It will be recognized that a variety of materials or structures could be used as a pop filter in conjunction with a noise mitigating microphone attachment. 
       FIG. 3  illustrates the insertion of elements such as a pop filter and microphone into noise mitigating microphone attachment structure  300 , according to an embodiment. Pop filter  302  may correspond to pop filter  200  described with reference to  FIG. 2 . Pop filter  302  can be inserted into opening  306  of structure  300 . The material of structure  300  may be resilient such that pop filter can be inserted within opening  306  of structure  300  and held in place relative to structure  300  by the material of structure  300 . 
     Microphone  304  can be inserted into microphone cavity  308  of noise mitigating microphone attachment  300 . The material of structure  300  may be resilient such that different sizes of microphones can be accommodated by microphone cavity  308 . In some embodiments, when microphone  304  is inserted into opening  308  of structure  300 , the material of structure  300  elastically couples noise mitigating microphone attachment  300  to microphone  304 . If a base of microphone  304  is too narrow to fit snugly within opening  308 , an insert, such as a foam collar insert, may be placed around the microphone casing. In this manner, the diameter of the microphone base may be increased such that the microphone base can fit snugly within opening  308 . When microphone  304  is inserted in opening  308 , elastic coupling between the casing of microphone  304  (or a collar tightly secured around microphone  304 ) and opening  308  may form a seal. The seal can reduce the amount of noise that enters the sound cavity through the microphone cavity. In some embodiments, the elastic coupling between microphone  304  and opening  308  can allow the noise mitigating microphone attachment to be suspended from microphone  304  (i.e., as if  FIG. 3  were rotated  180  degrees). 
     Microphone  304  can include sound receiving elements  310  and casing  312 . Microphone  304  can be any of a wide variety of microphones. The microphone type may be, for example, condenser, electret condenser, dynamic, etc. Typically, microphone  304  is a microphone designed for use in a recording studio environment, although it will be recognized that other microphones may be used. Microphone  304  may have any polar pattern, such as omnidirectional, cardioid, hypercardioid, supercardioid, etc. 
     The noise mitigating microphone attachment can improve the performance of an omnidirectional microphone for recording performance sound. As will be recognized by those skilled in the art, an omnidirectional microphone may be undesirable when a microphone is used for recording a performance from a particular sound source, such as a vocal performance, because the omnidirectional microphone will pick up sound arriving directly from the vocalist and sound from other directions (e.g., environmental noise and reflected sound from the performance sound source) approximately equally. In contrast, when a noise mitigating microphone attachment is used with an omnidirectional microphone, the noise mitigating microphone attachment receives direct performance sound via the sound cavity and can attenuate and/or absorb sound arriving from other directions. 
       FIG. 4  is a front view  400  of a noise mitigating microphone attachment shown seated in a shock mount, according to an embodiment. In some embodiments, noise mitigating microphone attachment  402  can be seated in a shock mount  404 . A shock mount is a mechanical fastener that can suspend a microphone in elastics that are attached to a microphone stand such that transmission of vibrations from the microphone stand to the microphone is minimized. The shape of the noise mitigating microphone attachment allows it to be used with a microphone mounted in a shock mount. The noise mitigating microphone attachment can also be used with a microphone mounted directly to a microphone stand. 
     To mount noise mitigating microphone attachment  402  within shock mount  404 , the noise mitigating microphone attachment  402  is seated within a cradle formed by the upper arms of shock mount  404 . In this manner, the noise mitigating microphone attachment  402  is held in place relative to shock mount  404  by gravity. 
       FIG. 5  is a flowchart of a process  500  for channeling sound during a recording with a noise mitigating microphone attachment, according to an embodiment. 
     At block  502 , a microphone can be inserted into a first opening, such as opening  110  of microphone cavity  108 , of a noise mitigating microphone attachment  100 . At block  504 , the microphone can be extended through first cavity  108  into a second cavity, such as sound cavity  104 , of the noise mitigating microphone attachment  100 . At block  506 , a performance sound source, such as the mouth of a vocalist, can be positioned proximate to a second opening, such as opening  106 , of the noise mitigating microphone attachment. At block  508 , the microphone can be used to record sound waves from the performance sound source that enter the second cavity via the second opening. 
     The embodiments described herein provide a portable device that can be produced at low cost relative to the cost of existing solutions for noise mitigation in recording environments. The noise mitigation microphone attachment can be used for sound recording in a home studio, outdoors, or other environment to protect a microphone from picking up unwanted sounds during a performance. A microphone can be inserted into a first opening of the noise mitigation microphone attachment and extend through a microphone cavity into a sound cavity. The sound cavity can extend from a second opening at the surface of the noise mitigating microphone attachment. A performance sound source is typically located proximate to the second opening. Sound incident on the exterior of the noise mitigating microphone attachment is attenuated by the structure of the noise mitigating microphone attachment. 
     While the invention has been described with respect to specific embodiments, one skilled in the art will recognize that numerous modifications are possible. Thus, although the invention has been described with respect to specific embodiments, it will be appreciated that the invention is intended to cover all modifications and equivalents within the scope of the following claims.