WO1988008657A1

WO1988008657A1 - Procedure and device for facilitating audiovisual observation of a distant object

Info

Publication number: WO1988008657A1
Application number: PCT/FI1988/000060
Authority: WO
Inventors: Esko Alasaarela; Pekka Adolfsen; Timo Rahkonen
Original assignee: Utk Uuden Teknologian Keskus Oy
Priority date: 1987-04-23
Filing date: 1988-04-22
Publication date: 1988-11-03
Also published as: US5007091A; JPH02503849A; FI77347B; FI871793A0; EP0363376A1; FI77347C

Abstract

Device for listening to and recording of the sounds produced by birds or other distant objects. The device is attached to a pair of binoculars or a telescope and consists of one or more directional microphones, microphone structures or sets of microphones, a microphone and headphone amplifier and a pair of headphones, the directional microphone structures (2, 3) and the amplifier unit (4) with the headphones (7) being attached to the binoculars (1) by suitable means. An audio signal can be supplied from the amplifier to an external recording device, or a recording device may be integrated with the device of the invention. Used together with a pair of binoculars or a telescope, the device provides a light and easy-to-use means of audiovisual observation of distant objects, and when provided with an integral or external tape recorder it is also suited for amateur use for the recording of wildlife sounds.

Description

PROCEDURE AND DEVICE FOR FACILITATING AUDIOVISUAL OBSERVATION OF A DISTANT OBJECT

The invention concerns a listening device for supervision or wildlife observation purposes, said device being mounted on a pair of binoculars or a telescope and provided with means for electronic amplification of sound.

The objects to be observed or supervised are generally at a distance necessitating the use of binoculars or a telescope and a directional sonic detector with an amplifier. Sometimes it is also necessary to record the sounds produced by the object observed (e.g. when a strange bird is to be later identified on the basis of its utterings). Among the most commonly used lis¬ tening and recording devices is the parabolic reflector, which is about 1 m in diameter and is used with an amplifier and a recording device, but such a reflector is difficult to. irect accurately. US patent 3 881 056 proposes an apparatus using a hand-held parabolic reflector of a diameter of about 45 cm, which is somewhat easier to handle but is still very difficult to use together with binoculars. Of the numerous other types of directional microphones (e.g. US patents 4 401 859, 3 793 489, 3 715 500, 3 657 490 or 4 421 957), none has become widely accepted for use in wildlife observation.

There is a Norwegian patent (No. 21869) of the year 1911 which proposes a hearing aid that is mounted on opera glasses. The hearing aid consists of trumpets placed around the objectives of the opera glass, with the trumpet opening in the forward direction, the sound being passed from the rear end of the trumpet to the user's ears via hose pipes like those of a stethoscope.

There are various hearing aids (e.g. US patents 3 983 336, 3 665 121, 3 770 911) which can be used together with binocu¬ lars. However, they are not designed for use by people with normal hearing and have no provision for the recording of sound. Besides, hearing aids mounted on the spectacle frame are difficult to use together with binoculars.

There are several types of microphones of integral construction which are designed for use with narrow-film cameras or video cameras, e.g. US patent 3 837 736 (Camera and microphone having variable directional characteristics in accordance with a zoom lens control) . These microphones are generally designed to be directionally selective in the first place with regard to acoustic signals recorded indoors from a distance of a few metres, so that the sensitivity of the microphone and amplifier is not sufficient for the recording of weak sounds from a long distance. Although the microphones used in connection with nar¬ row-film or video cameras are applicable for recording and lis¬ tening purposes, the visual perception obtained through the view-finder of the camera is not comparable in brilliance and sharpness to the image provided by binoculars or a telescope - the cameras often use ground-glass view-finder lenses with in¬ ferior contrast and luminous efficiency. Besides, the cameras are mainly designed for the recording of images (and sound) and not for audiovisual observation as in the case of the present invention„

The recording equipment currently used in wildlife observation faces the user with many problems due to the large size and weight of the directional microphone and tape recorder. The sizeable directional microphone is also sensitive to structure- borne noise, necessitating the use of a stand. In addition to the audio recording equipment, a separate telescope or a pair of binoculars is needed to enable the object to be located, but since the directional settings of the two observation devices have to be adjusted separately - a task requiring great accuracy - simultaneous visual and acoustic observation is dif¬ ficult. The combination of an opera glass and an ear trumpet proposed by the NO patent No. 21869 comes closest to the idea of the present invention, but as a purely mechanical construc¬ tion it is clearly not suited for recording purposes and it has no provision for volume or tone control. In outdoor use the trumpets _are sensitive to wind noise and the device is incon¬ venient to use because of the stethoscope pipes required. All these drawbacks are eliminated by combining an electronic am¬ plifier with a pair of binoculars, which makes it possible to process the acoustic signal in a variety of ways, resulting in a decisive improvement in sound quality. For instance, low-fre¬ quency structure-borne and wind noise can be filtered out, and an enhanced stereo effect can be created to facilitate the directional adjustment.

The device of the invention provides decisive improvements re¬ garding the drawbacks mentioned above. To achieve this, the de¬ vice of the invention is characterized as specified in claim 1. The chief advantages of the invention are the integral con¬ struction of the listening device and the viewing devic (binoculars or telescope), the ease of directional adjustmen and the small size, light weight and versatility of the device as compared to conventional audio recording devices used in wildlife observation.

In the following, the invention is described in detail with reference to the drawings attached.

Fig. 1 Device of the invention, mounted on a pair of binoculars.

Fig. 2 Example of a quick attachment system enabling the device to be detached and fitted to different types of binocu¬ lars or telescopes.

Fig. 3 Device of the invention, mounted on a telescope and used for sound recording.

Fig. 4 Example of foldable directional microphones and integral headphones.

Fig. 5 Example of achi-eving an improved radiation pattern via appropriate positioning of the microphones.

Fig. 6 Radiation patterns obtained by the arrangement in fig. 5

Fig. 7 Block diagram of the electronics used in the device.

In the following examples, the directional microphone elements are small parabolic reflectors. It is to be noted that the device of the invention may use any other kind of directional microphone structure suited for the purpose.

Fig. 1 shows the device of the invention as mounted on a pair of binoculars 1, consisting of two parabolic reflectors 2, the reflected sound signal being converted into an electrical form by means of suitable microphone capsules 3. The microphone signals are passed into an amplifier 4 where the signals are amplified and processed as desired. The amplified signal is output via a headphone connection 5, where a pair of headphones 7 is plugged in for simultaneous listening. For recording, the amplified signal is obtained from a separate recording connec¬ tion 6. For listening and recording, there is a volume control 8 and a tone control 9. In addition, the directional and stereo effects can be adjusted with a selector switch 10.

Fig. 2 illustrates a possible arrangement for quick attachment of the device on a pair of binoculars. The parabolic reflector 20, provided with a microphone capsule 21, is attached to one of the objectives 22 of the binoculars by means of a strap 24 which is tightened around the objective. That side of the reflector which is pressed against the objective is provided with, cushion pads 23 which adapt to the curvature of the objec¬ tive surface and act as friction grips keeping the reflector in position relative to the objective. The strap 24 is provided with locking studs 25 which are engaged by a locking link 27 pivoted on a locking lever 26 , shown in its open position in the drawing. When the locking lever 26 is turned into the posi¬ tion indicated by dotted lines, the strap is tightened and the cushion pads 23 are pressed tightly against the side of the objective. By using a long enough strap provided with a suffi¬ cient number of locking studs 25, the device can be mounted on binoculars and telescopes of widely differing sizes and types.

Fig. 3 illustrates the device of the invention as mounted on a telescope and used for the recording of sound. The telescope 30 is attached to a stand 37, and the reflectors, 31 provided with microphones 32, are attached to the telescope. The amplifier 33 is placed on top of the telescope, a portable tape recorder 34 being plugged into the appropriate connection 36 of the ampli¬ fier. When a recorder is used, the headphones 35 are preferably connected to the recorder's headphone socket . for tape monitoring.

Fig. 4 shows certain solutions facilitating the transportation of the device. The binoculars 40 are provided with parabolic reflectors 41 , an amplifier 42 and headphones 43. The reflec¬ tors are pivoted in front of the binoculars so that they can be folded up to protect the objectives. The headphones may like¬ wise be^" integrally constructed and they can also be folded up to protect the lenses, or they can be provided with telescopic arms which can be collapsed for transport, so that the dimen¬ sions of the binoculars will not be significantly increased by the headphones. Fig. 5 is an example of positioning the directional microphon structures in such a way that when the microphone signals ar directed so as to obtain a monophonic response, the main beam in the radiation patterns of the microphone structures wil strengthen each other but the side beams will not be summed i the same direction. The figure shows the binoculars in fron view, with reference number 50 indicating the right-hand objec tive, 51a and 51b right- and left-hand microphone structures, and 52 the amplifier unit.

Fig. 6 represents the radiation pattern, also seen from th front, of the device as shown in fig. 5. 60b is the main bea in the radiation pattern of the right-hand microphone struc¬ ture, 60a the corresponding beam of the left-hand microphone structure, and 61a and 61b the side beams of the right- and left-hand microphone structures respectively. As seen from the figure, the asymmetric side beams do not fall in the same place and therefore do not strengthen each other.

Fig. 7 shows a block diagram of the electronics used in the device of the invention. The microphones 70 of the right and left channels are connected to the corresponding microphone amplifiers 71 , followed by a summing unit 72 whose operation can be varied, as explained later, by means of a switching or control unit 73. From the summing unit, the signal is taken to the recorder connection 74 and to headphone amplifiers 75 and further to the headphone connection 76.

The summing unit 72 provides the options of e.g. a fully stereophonic response (the signals of the two microphones do not affect each other), a spatial (electronically enlarged) stereo effect to facilitate the directing of the microphone structures, a fully monophonic response, which means that iden¬ tical signals are supplied to both headphones and that the ra¬ diation pattern of the microphone set consisting of the direc¬ tional microphones is sharpest and the noise at a minimum, or frequency-dependent summation in such manner that low frequen¬ cies up to a given limit are summed to produce a monophonic response while higher frequencies are reproduced stereophoni- cally. One of the advantages of the latter option is that when small-size directional microphone structures with a poor low-frequency directivity are used, a good radiation pattern is obtained even for low-frequency sounds while a stereo effect is still preserved to facilitate location of the object. At the same time, this prevents the radiation pattern of high-frequen¬ cy sounds from becoming too narrow and the side beams from becoming too strong.

In the examples used to describe the invention, the directional microphone element consists of two small parabolic reflectors, but it is possible to use any other microphone structure that suits the purpose. Possible alternatives are e.g. a microphone surface consisting of a suitable acoustically sensitive mem¬ brane (such as a film of pvdf-material, or an electrothermome- chanical film as developed at Tampere University of Techno¬ logy) , a set of several microphones, a gradient microphone and a tubular microphone with one or more tubes. Also, instead of a parabolic reflector, a reflector or trumpet of a different form may be used. In addition, the microphone structures can (and should) be provided with suitable windshields. It is to be noted that, depending on the microphone structure selected, the device can be attached to the binoculars or telescope in vari¬ ous ways, so the attachment mechanism illustrated in fig. 2 is by no means an exclusive possibility.

If necessary, the sound volume and tone controls can be coupled to the focusing control of the binoculars to provide for auto¬ matic compensation of the damping, especially of high frequen¬ cies, caused by a long distance. The controls can be implement¬ ed using a solution that seems best, e.g. rocking-switch con¬ trols, which will not be easily confused with the generally rotatable focusing control of the binoculars. If the view angle of the optical device can be adjusted (zoomed), then the radia¬ tion pattern of the directional microphones can be adjusted accordingly (cf. US patent 3 837 736).

In addition to the functions mentioned above, the amplifier electronics may include filtering functions to correct the microphone response or the damping of high frequencies caused by the atmosphere, or noise reduction by suitably limiting the passband (e.g. by setting the lower limiting frequency at 100 - 300 Hz). Automatic gain control may be used arid the distortion caused by strong sound signals may be reduced by means of amplitude limiters or soft-clipping circuits. If the signal-to-noise ratio and the wide dynamic range of natural sounds cause problems, compression may be used to level the variations in signal strength. The signal output for recording may be provided with a level control to enable any commercial recording device (e.g. portable mini-recorders) to be connected to the amplifier. If necessary, a recording device may be inte¬ grated with the amplifier, in which case the two devices can use a common power supply, and if desirable for reasons of con¬ venience (weight of the equipment), the amplifier and recorder may be constructed as a separate unit to be carried on a shoul¬ der strap while only the light-weight directional microphones are mounted on the binoculars or telescope.

The device of the invention may be powered either by batteries, an accumulator or solar cells. There is ample space for solar cells e.g. on the backside of the parabolic reflectors. The device may have a provision for the connection of an external power supply to allow the recharging of batteries or the use of a separate power source, e.g. that of a tape recorder.

Claims

1. Procedure for audiovisual observation of distant objects by simultaneously watching the object by means of a viewing device such as a pair of binoculars or a telescope and listening to the object by means of a listening device, c h a r a c t e r ¬ i z e d in that the procedure involves the use of two micro¬ phones or sets of microphones, which are acoustically or elec¬ tronically so connected that, via signal processing, a number of effects are achieved, of which one of the following applies: a) the headphone signal . is monophonic, in which case the directivity is best; b) the headphone signal is stereophonic, facilitating the task of locating the source of the sound; c) a spatial stereophonic effect in the headphone signal is produced ^" by using a suitable electronic connection, thus further facilitating the task of locating the object; d) the signals from the microphones or sets of microphones are processed in a frequency-dependent manner, so that the headphone signal is monophonic at low frequencies to improve directivity and stereophonic at high frequencies to facilitate location of the object.

2. Device for implementing the procedure of claim 1, consisting of a listening device attached to the optical device, e.g. a pair of binoculars or a telescope, and including a microphone or a set of microphones (2).having a suitable directional capa¬ bility, and an amplifier unit (4) to which suitable headphones (7) can be connected, c h a r a c t e r i z e d in that the device comprises at least two microphones or sets of micro¬ phones whose output signals can be acoustically or electroni¬ cally so connected that one of the following applies: - a) the headphone signal is monophonic, in which case the directivity is best; b) the headphone signal is stereophonic, facilitating the task of locating the source of the sound; c) a spatial stereophonic effect in the headphone signal is produced by using a suitable electronic connection, thus further facilitating the task of locating the object; d) the signals ^' from the microphones or sets of microphones are processed in a frequency-dependent manner, so that the headphone signal is monophonic at low frequencies to improve directivity and stereophonic at high frequencies to facilitate location of the object.

3. Device according to claim 2, c h a r a c t e r i z e d in that the amplifier unit is provided with sound volume and tone controls which are connected to the focusing control of the binoculars or telescope in an optimal manner so that the gain or the tone, i.e. dependency on frequency, of the amplifier depends on the focusing adjustment of the binoculars or tele¬ scope in such manner that the damping caused by a long listen¬ ing distance in the sound or, in the case of tone controls, in the high-frequency sounds, is partially or totally compensated.

4. Device according to claim 2 or 3, c h a r a c t e r i z e d in that the continuous manual volume control of the amplifier unit is corrected by automatic gain control, or the amplifier is provided with a limiter or compressor to avoid excessive signal amplitudes.

5. Device according to any one of the above claims, c h a r ¬ a c t e r i z e d in that the headphones are of an integral construction so that they can be collapsed or folded up to act as lens protectors.

6. Device according to any one of the above claims, c h a r - a c t e r i z e d in that the microphone or set of microphones consists of an integral surface or reflector which can be folded e.g. in the manner shown in fig. 4 to act as a lens protector.

7. Device according to any one of the above claims, c h a r ¬ a c t e r i z e d in that it is provided with an integral tape recorder for the recording of sound or with a recorder connec¬ tion for an external audio recording device, the signal level in said recorder connection being adjustable to accommodate different types of tape recording devices.

8. Device according to any one of the above claims, c h a r ¬ a c t e r i z e d in that the amplifier is a separate unit or integrated with a separate tape recorder or audio recording device, the headphones being connected to the amplifier.

9. Device according to any one of the above claims, c h a r ¬ a c t e r i z e d in that the element used for the reception of sound is one of the following: a) Parabolic reflector or other kind of reflector or trumpet of a suitable form, provided with a microphone of a type that best fits the purpose; b) A set of microphones or a microphone surface whose radiation pattern is suitably adjusted by amplifying the signals obtained from different parts of the set in different ways; c) One of the previous alternatives using microphones of a type or construction that in itself improves the directivity and the damping of background sounds.