WO2004082328A1 - Mini microphone - Google Patents

Abstract

A mini microphone consists of a microphone housing (1) and a connector means (2). In the walls of the microphone housing there are openings (3,4) with sound sensors for picking up main sound, as well as further openings (5,6) with sound sensors for picking up external sound (noise), and the further openings (5,6) face in other directions than the main sound openings (3,4). The connector means (2) also constitute an attachment means for the microphone.

Description

MINI MICROPHONE

The present invention relates to a microphone, and in particular a small microphone of the type to be placed as close as practically possible to a sound emitter of current interest, for example a microphone in the form of a stick that protrudes along the cheek of a person, or a small microphone to be attached to a special stand on a musical instrument. This type of microphone will be referred to as a mini microphone in the following.

Mini microphones are commonly known, and they are used in particular in the entertainment industry, in television or in stage performances. The sound transducers of these microphones are small, and can even be produced in the size of a pinhead. This provides the possibility of producing microphones that are almost invisible to an audience.

However, like other microphones, such microphones will be exposed to picking up noise, and there will always exist a desire to reduce noise, to the benefit of a speech/song signal from a person, or sound emitted from an instrument, desired to be picked up and transferred as clearly and distinctly as possible. Previously known solutions regarding reduction of noise that has been picked up, which noise will be referred to in the following as "external sound" as opposed to the main sound from the sound emitter of interest, consist primarily in carrying out filtering of typical noise frequencies, or equipping the microphone with attenuating elements for e.g. wind noise. Further, directivity techniques have been used, i.e. to make the microphone "see" only in a direction toward the actual noise emitter, while sound from other directions is suppressed.

An example of such directivity technique appears in US patent number 4,399,327. In this case, the degree of directivity can be varied, in connection with use together with a zoom-equipped camera. To obtain this, three sound transducers are placed inside an elongate microphone housing, and two of the three transducers are directed in one direction, while the third transducer "sees" in the opposite direction. The signals from the three transducers are combined in a variable ratio, and this provides the variable directivity. However, the microphone of US 4,399,327 is no mini microphone, and it is not operative to pick up sound from a sound source in the immediate proximity, but is, by nature, made to be able to "zoom" in toward distant sound emitters.

Thus, a mini microphone designed as a stick and carried along the cheek of a person in order to pick up sound from the person's mouth, is nevertheless regarded as the closest prior art, since such a microphone has small dimensions and is adapted for close proximity pickup. However, such a microphone suffers from noise problems, such as mentioned introductorily.

Signal processing inside the very microphone is previously known from Norwegian patent application No. 2001 5983 which belongs to the proprietor of the present invention.

However, a need remains for providing noise-suppressed mini microphones, i.e. small microphones that give the possibility for suppressing external sound. The present invention aims at satisfying this need. Hence, in accordance with the present invention, there is provided a mini microphone which comprises a microphone housing with a first sound transducer arranged therein for picking up sound (main sound) from a sound emitter in the immediate proximity of the microphone, for instance from a person's organ of speech, and conversion of the main sound to an electric main signal conducted by a main signal line inside the microphone housing. The mini microphone in accordance with the invention is characterized in thai the microphone housing contains al least one further sound transducer for picking up external sound, and this further transducer is oriented in the microphone housing in a different direction than the first transducer, and gives off an electric secondary signal on a separate secondary line, and the signal lines end in a connector means which at the same time constitutes an attachment means to auxiliary equipment adapted for supporting the mini microphone close to the sound emitter.

In a preferred embodiment of the invention, the further sound transducer has a pickup direction situated at an angle 30-180° away from the pickup direction of the first sound transducer.

The signal lines from the microphone transducers may lead first to a signal processor built into the microphone, which signal processor undertakes noise reduction processing of the main signal on the basis of a comparison between this signal and the secondary signal. Alternatively, the signal lines from the microphone transducers may have a connection out of the microphone via the connector means to a signal processor in a body-carried radio transmitter, where the signal processor carries out noise reduction processing of the main signal on the basis of a comparison between this signal and the secondary signal.

In a favourable embodiment of the microphone in accordance with the invention, it includes at least one other sound transducer for picking up main sound, and the other sound transducer then has a different characteristic than the first mentioned sound transducer, for instance with regard to frequency response or directivity.

In another favourable embodiment, the respective sound transducers may be replaceable.

The auxiliary equipment can be selected from a set that comprises head bows, neck bows, ear bows, stands, clip devices for clothes attachment, head/neck/ear bows with sound processor, stands with sound processor, clip devices with sound processor, as well as corresponding elements with radio transmitter.

In a preferred embodiment, the microphone housing is elongate and made of a ductile material. At the same time, the connector means can be arranged at an end of the microphone housing.

In a more special embodiment, the microphone housing may be extendable, for instance with a telescopic construction.

In the following, the invention shall be illuminated further by going through some favourable and preferred embodiments, and in this connection it is referred to the appended drawings, where fig. 1 shows schematically an embodiment of a mini microphone in accordance with the present invention; fig. 2 shows such a microphone as in fig. 1 , attached to an ear bow so as to be carried along the cheek of a person; fig. 3 shows an example of an internal structure in a section of a mini microphone in accordance with the invention; and fig. 4 shows a mini microphone in accordance with the invention, mounted on a musical instrument. In fig. 1 appears a relatively simple version of a mini microphone in accordance with the present invention. An elongate microphone element 1 is equipped with small openings 3, 4, 5, 6 having, in different positions along element 1 , sound sensors/transducers arranged inside the openings (and in some cases protruding out therefrom). The microphone element 1 can also be regarded as a microphone housing that contains various devices that will be mentioned in the following. At a rear end of microphone element 1 there is arranged a connector means 2, and at an opposite forward end there is, in the embodiment shown, arranged two sensor openings 3, 4, which in this embodiment corresponds to two main sensors for picking up the sound that is of real interest, referred to as "main sound" in the following. This may be the voice of a person, or equally well, primary sound from a musical instrument. It should be noted that the microphone element just as well might have only one sensor opening at the front, i.e. only one sensor. But it is considered as favourable using for instance two sensors having separate and possibly overlapping frequency ranges, for instance 200-20 000 Hz for one and 20-500 Hz for the other, since it will often be simpler to use two specialized sensors, than one sensor for covering the complete hearing range. In line therewith, it may be of interest using even three or more main sensors.

In addition, the microphone element 1 has a number of additional sensor openings 5 along a longitudinal surface, and a further number of such openings 6 along another longitudinal surface. The drawing shows three and two such sensor openings respectively, but this is only an example. Furthermore, the design of the microphone element 1 does not need to be with a rectangular cross section such as in the drawing, the cross section may be many-cornered, oval or circular, so that the directions in which the sensor openings 5, 6 are facing, may be different from what appears in this drawing. In the drawing, the main sensors 3, 4 listen toward the "main sound", noting that if the mini microphone shall be used such as shown in fig. 2, that is as a cheek-worn microphone, the main sensors 3, 4 will be situated at the front end but at the "inside", i.e. the non-visible side in fig. 1 , or the front end will be bevelled toward the inside, possibly at the same time as having element 1 bent somewhat inwards near the front. The microphone element 1 is preferably made of flexible material, for instance plastic material.

But with an embodiment such as shown in fig. 1 , it appears that the sensor openings 5 face in a direction that is about 90° different from the main sensors 3, 4, i.e. "right outwards" if the shown element 1 engages a cheek with its backside, and sensor openings 6 face also in a direction about 90° differently from the main sensors 3, 4, however in an up direction. Using for instance an oval cross section shape, other listening directions can be provided for the additional sensors 5, 6. And with a different angling for the main sensors 3, 4, such as mentioned above, the angle deviations to the additional sensors become different - for instance, the angular deviation to sensors 5 would be 180°, if the main sensors 3, 4 were arranged on the backside/inside such as mentioned above.

In other words, it is an important point that the additional sensors 5, 6 face/listen in other directions than the main sensors 3, 4, using an angular deviation of at least about 30°. Sound picked up by these additional sensors 5, 6 will comprise a larger contribution from "external" sound, i.e. sound which in the current context often must be considered as noise. These "external sound signals" from additional sensors 5, 6 can be used in a sound processor for treating the main signals from main sensors 3, 4, just for elimination of noise picked up by the main sensors 3, 4.

In one simple embodiment, conductors run internally in the microphone housing 1 from each sensor 3-6 back to the connector means 2, which connector means primarily provides a connection for further transmission of the signals, and additionally provides support/attachment for the microphone element 1 in use. Fig. 2 shows how the microphone element 1 can be attached to an ear bow 8 designed for attachment to a person's ear, and in such a manner that the microphone element 1 runs flush forward along the person's cheek so that a main sensor (or several such sensors) arranged at the front, can pick up main sound from the person's mouth, while (not shown) additional sensors pick up external sound, i.e. noise from the surroundings. Signals from the various sensors are conveyed out via the connector means 2 through a complementary connector means/attachment means 7 on the ear bow, and further to processor equipment or radio transmitter equipment inside the ear bow 8, or possibly further through a (not shown) wiring from the ear bow 8 to another unit possibly worn on the person's body.

Furthermore, in fig. 2 appears a special detail of an embodiment of the mini microphone of the invention, namely the possibility of making the microphone element 1 extendable, such as shown here by reference numeral 23, in the form of a telescopically sectioned and slideably extendable microphone element. The inside wiring may then arranged with sliding contact springs, spiral-wound conductors or conductors with sufficient slack. Other embodiments regarding a support means such as the ear bow 8, may be a head bow, a neck bow, a clip to be attached to a jacket collar or similar, or a clip or stand for attachment for instance to a musical instrument, such as shown in fig. 4: in this figure appears a wind instrument 21 which has mounted thereon a mini microphone in accordance with the invention. A stand 22 is attached to the edge of the horn bell, and has a complementary connector 7 to which the connector means 2 can be attached and be connected to, in such a manner that the microphone element 1 is brought to a desired position. This means a position with arrangement of main sensor(s) for picking up a main sound signal from the instrument in a favourable position, and with additional sensors directed to the surroundings for picking up a larger part of external sound. The position shown in the drawing is of course merely for illustration, skilled persons with experience in the field of microphony will have knowledge of the correct and interesting positions for such microphones, or such positions will be found after some experimentation.

Fig. 4 shows schematically some of the insides of an embodiment of a mini microphone in accordance with the invention, presenting a sort of "X-ray view" through a section of a microphone element of a similar type as in fig. 1 , i.e. somewhat toward the left hand end of the microphone element shown in fig. 1.

Starting from the sensor openings 5 (for simplicity, no opening 6 is shown in this drawing), small sensor units 9 appear just inside each such opening. The "earth" pole of each sensor is connected via conductor 10 to a common "earth" conductor 11 , which leads to a low input on a built-in microprocessor 16 in the microphone element near the end connector 2 (which is only suggested in the drawing). The microprocessor 16 is powered by a battery 20 (the dimensions of respective units are not drawn to scale).

The active poles on each sensor unit 9 are connected to the microprocessor through respective conductors 12, 13 14, 15 leading to respective inputs, shown in general by reference numeral 19 on the microprocessor. Then, after treatment, a ready processed signal is output on the conductor pair 17 that leads to connector 2.

Hence, fig. 3 shows an embodiment of a relatively advanced type, with a built-in processor 16. However, in general, microphone element 1 does not need any such built-in processor, the relevant number of conductors may in other embodiments run directly to the connector means 2, which in such case has a corresponding number of poles in order to convey the respective signals further to a contact/attachment means of suitable type. This attachment means may comprise electronic circuitry for signal processing and/or radio transmission, or it may be connected by wiring to a next unit that may contain the necessary processing equipment for treatment of the signals in order to provide a noise-free main signal (or for that matter, a main signal that has been subjected to desired effects).

In one favourable embodiment of the microphone, the construction of the microphone housing/element 1 is such that the sensors 9 inside openings 3, 4, 5, 6 can be replaced, either in order to use other sensors with different characteristics, or possibly in order to replace a broken sensor. In such a case, the microphone construction may include a connector means 2 that can be snapped on and off, i.e. it can be pulled off with a jerk. Further, the insides of the microphone element 1 are then in sections, and can be pulled out through the opening that accommodated the connector means 2, with all sensors, and the sensors may then be replaced one by one if necessary.

In another favourable embodiment, the microphone element is made of plastic material that is to a certain degree ductile, so that a final adjustment of the sensor positions may be made simply by bending or twisting the element a little.

There will not always exist a need to use all sensors in a finished microphone that provides the possibility of for instance two main signals and five external signals, such as shown in fig. 1. It may happen that one main sensor and one single additional sensor "do the job" in a certain situation. However, this can be arranged in a simple manner just by omitting use of the other signals conveyed to the processor in question. Another manner of achieving the same, may be removal of sensor units that are not of interest, if the microphone unit is of a type having replaceable sensors.

Production- and marketing-wise it may be an advantage to provide a certain degree of standardization, and a first level would be a standardized connector 2 with a corresponding assortment of attachment means with a complementary standardized connector 7.

A next level may be a standardized microphone element/microphone housing with a fixed layout regarding sensors, but where the current microprocessor is commanded to select the sensors that are of interest in one particular application. In other words, one visualizes use of the same standardized microphone element in many different connections, both for speech, song and various instrument applications, but then with a selection of relevant sensors for each particular situation.

The length of a typical microphone element of elongate type in a microphone in accordance with the invention, may preferably be in the range 3-15 cm. In some applications, it may be favourable that the microphone element has on one of its sides an adhesive layer to provide attachment to a surface.

As previously mentioned, the sensors that are used are small, and they may generally have a cylindrical shape, with a diameter in the mm range, often in the range 2-6 mm, typically 4 mm, and a similar cylinder height. Many suppliers can provide such sound sensors, and the sensors work according to various principles. Dynamic sensors, crystal sensors, capacitor and electret elements as well as piezo- ceramic elements are in the trade. Additionally, one may mention piezoelectric sensors of a type that has been presented by the proprietor of the present invention, in Norwegian patent No. 312.792. These sensors can also be constructed with sufficiently small dimensions to be used in a microphone in accordance with the present invention. Besides, the dimensions of the cylindrically designed sensor elements (height relative to diameter) are related to the self-directivity of the sensor element, i.e. sensitivity with regard to directional deviation from the listening axis. However, the directivity of each such element will also be influenced by how it is mounted in the opening 3-6, since the self-directivity will be maintained if the sensor element is mounted flush with the outer surface of the microphone element, while the listening space angle will be less if mounted further inside the opening.

Furthermore, there is a possibility of supplementing such a mini microphone as the invention relates to, with a vibration sensor for certain applications. It may, for instance in an application such as shown in fig. 4, be of special interest to pick up vibrations transmitted through the body of the very sound emitter, i.e. in the horn wall, directly by sensing through engagement to the body. For this purpose, the microphone may have a small sensor protruding somewhat on one of its sides, of the type accelerometer sensor or vibration sensor. Such sensors can be found also in the trade, but the proprietor of the present invention discloses such a vibration sensor also, in Norwegian patent No. 306.926.

Finally, a possibility must be mentioned for one or several of the sensors to be two- way transducers with the ability to transmit and receive sound or ultrasound for instance with regard to range measurement such as disclosed in the proprietor's PCT application with publication No. WO 02/00117, in addition to the normal sound sensor function. Useful extra information can be gathered from such ultrasound signals, for instance superposed noise information, which can be applied in the processing of the main sound signal.

Claims

1. A mini microphone comprising a microphone housing with a first sound transducer arranged therein for picking up sound (main sound) from a sound emitter in the immediate proximity of the microphone, for instance from the speech organ of a person, and converting the main sound to an electrical main signal conveyed on a main signal line inside the microphone housing, characterized in that the microphone housing contains at least one further sound transducer for picking up external sound, said further transducer being oriented in the microphone housing in a different direction than the first transducer, and delivers an electrical secondary signal on a separate secondary line, and that the signal lines end in a connector means that at the same time constitutes an attachment means to an auxiliary equipment operative to support the mini microphone close to the sound emitter.

2. The mini microphone of claim 1 , characterized in that the further sound transducer has a pickup direction oriented at an angle that is in a range 30-180° away from the pickup direction of the first sound transducer.

3. The mini microphone of claim 1 , characterized in that the signal lines from the microphone transducers first lead to a signal processor built into the microphone, said signal processor undertaking noise reduction processing of the main signal on the basis of a comparison between the main signal and the secondary signal.

4. The mini microphone of claim 1 , characterized in that the signal lines from the microphone transducers have connection out of the microphone via the connector means to a signal processor in a body-worn radio transmitter, said signal processor undertaking noise reduction processing of the main signal on the basis of a comparison between the main signal and the secondary signal.

5. The mini microphone of claim 1 , characterized in that it includes at least one second sound transducer for picking up main sound, said second sound transducer having a different characteristic than the first mentioned sound transducer for instance with regard to frequency response or directivity.

6. The mini microphone of claim 1 , characterized in that the respective sound transducers are replaceable.

7. The mini microphone of claim 1 , characterized in that the auxiliary equipment is selected from a set that comprises head bows, neck bows, ear bows, stands, clip devices for garment attachment, head/neck/ear bows with sound processor, stands with sound processor, clip devices with sound processor, and corresponding elements with radio transmitter.

8. The mini microphone of claim 1 , characterized in that the microphone housing is elongate and made of a ductile material.

9. The mini microphone of claim 8, characterized in that the connector means is arranged at an end of the microphone housing.

10. The mini microphone of claim 1 , characterized in that the microphone housing is extendable, for instance by means of a telescopic construction.

11. The mini microphone of claim 1 , characterized by an additional transducer arranged to pick up vibrations in a sound emitter body by direct engagement thereto.