Abnormal sound detecting apparatus

Abstract: An abnormal sound detecting apparatus includes at least one acoustoelectric conversion element (1a) for converting an acoustic pressure into an electrical signal, two amplifiers (3R, 3L) for amplifying the electrical signal from the acoustoelectric conversion element (1a), and two volume controllers (2R, 2L) respectively provided at the input sides of the two amplifiers (3R, 3L) for controlling the electrical signal from the acoustoelectric conversion element (1a). A change-over switch (4) selectively supplies the electrical signal from the acoustoelectric conversion element (1a), or from a selected one or a selected combination of elements, to the two amplifiers (3R, 3L) via the two respective volume controllers (2R, 2L), and a stereophonic headphone (5) may receive the output signals from the two amplifiers (3R, 3L) to convert the signals to sound; alternatively or additionally to the headphone (5), a sound level meter (10) may be provided.

Description: The present invention relates to apparatus for detecting abnormal sounds, such as sounds emitted from parts of a motor vehicle which may be moving, for example sounds from the engine, injector(s), bearing(s), or an air conditioner. In order to detect a sound, for example an abnormal sound emitted from a motor vehicle, it has previously been necessary to use a detecting device similar to a stethoscope. Since the mechanical details of motor vehicles are becoming increasingly complicated, it is very difficult for such a detecting device using the principle of the stethoscope to detect or find an abnormal sound and hence its source in the motor vehicle. Further, the detecting device using the principle of the stethoscope cannot readily detect an abnormal sound which is most likely generated in a moving vehicle, such as an abnormal sound emitted from the suspension parts of the moving vehicle, its transmission mechanism, its differential gears, or other such rotating parts. Previously, when it has been required to detect such abnormal sounds occurring in a moving vehicle, it has been necessary for a mechanic to enter the boot of the vehicle or to ride on the back seat or front passenger's seat of the vehicle to listen to the abnormal sound and then find its source depending on the mechanic's perception and experiences while repeating the running test of the vehicle. Therefore, this inspection and detection of abnormal sounds and their source has required much time and skill. German Patent Application No. DE-A-1 673 911 discloses an abnormal sound detecting apparatus comprising: at least two acoustoelectric conversion means, each for converting an acoustic pressure into a respective electrical signal; first amplifying means for amplifying the electrical signal from said acoustoelectric conversion means; first volume control means for controlling the electrical signal from said acoustoelectric conversion means; change-over switching means for changeably supplying the electrical signals from said acoustoelectric conversion means to said first amplifying means and said first volume control means; and monitoring means responsive to output signals from said first amplifying means. According to the present invention there is provided an abnormal sound detecting apparatus as set out above, characterised by: second amplifying means; and second volume control means; wherein said change-over switching means is operable to supply changeably the electrical signals from said at least two acoustoelectric conversion means to said first and second amplifying means and to said first and second volume control means, and wherein said monitoring means is responsive to output signals from both said first and second amplifying means. In a preferred embodiment of the invention, the monitoring means can be in the form of a stereophonic headphone and/or a sound level meter. Accordingly, the preferred embodiment of the invention can provide an abnormal sound detecting apparatus which is free from the disadvantages encountered in the previous technique. The preferred apparatus can detect an abnormal sound and then find its source efficiently and accurately in a short period of time. The invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references, and in which: FIG. 1 is a connection diagram showing an abnormal sound detecting apparatus according to an embodiment of the present invention; FIG. 2 is a perspective view showing an example of a vibration sensor used in the embodiment shown in FIG. 1; FIGs. 3 and 4 are perspective views showing other examples of vibration sensor to be used in the embodiment shown in FIG. 1; FIG. 5 is a schematic diagram of one type of vibration sensor connection; FIG. 6 is a perspective view showing a main body of the embodiment shown in FIG. 1; and FIG. 7 is a schematic diagram used to explain one application of the present invention. FIG. 1 is a connection diagram showing an abnormal sound detecting apparatus according to an embodiment of the present invention. In this embodiment, for example, four acoustoelectric conversion elements (hereinafter referred to as vibration sensors) la, 1b, 1c and 1d are employed. Each of the vibration sensors 1a to 1d serves to convert a sound (acoustic pressure) into an electrical (voltage) signal and is made of, for example, a piezoelectric element. That is, each of the vibration sensors 1a to 1d produces an electrical signal whose frequency corresponds to the frequency of vibration or sound picked up by each of the vibration sensors. As shown in FIG. 1, in this embodiment an output electrical signal from the vibration sensor la is supplied through a lead wire to first one and first other fixed contacts 4a1 and 4a2 and to a fifth one fixed contact 4e1 of a change-over switch 4; an output electrical signal from the vibration sensor 1b is supplied through a lead wire to second one and second other fixed contacts 4b1 and 4b2 and to a fifth other fixed contact 4e2 of the change-over switch 4; an output electrical signal from the vibration sensor lc is supplied through a lead wire to third one and third other fixed contacts 4c1 and 4c2 and to a sixth one fixed contact 4f1 of the change-over switch 4; and an output electrical signal from the vibration sensor 1d is supplied through a lead wire to fourth one and fourth other fixed contacts 4d1 and 4d2 and to a sixth other fixed contact 4f2 of the change-over switch 4, respectively. The change-over switch 4 has one movable contact 4R which is changeably and successively connected to the one fixed contact 4a1, 4b1, 4c1, 4d1, 4e1 and 4f1 and, also has the other movable contact 4L which is changeably and successively connected to other fixed contacts 4a2, 4b2, 4c2, 4d2, 4e2 and 4f2. In this embodiment, the one and the other movable contacts 4R and 4L of the change-over switch 4 are manually switched over in a ganged relation. In this change-over switch 4, there are respectively provided ground contacts 4gl for grounding the one movable contact 4R between adjacent one fixed contacts, that is, between first and second one fixed contacts 4a1 and 4b1; second and third one fixed contacts 4b1 and 4c1; third and fourth one fixed contacts 4c1 and 4d1; fourth and fifth one fixed contacts 4d1 and 4e1; and fifth and sixth one fixed contacts 4e1 and 4f1, respectively, and the five ground fixed contact 4g1 are connected in common to the ground. Further, in the change-over switch 4, there are respectively provided other ground fixed contacts 4g2 for grounding the other movable contact 4L between adjacent other fixed contacts, that is, between first and second other fixed contacts 4a2 and 4b2; second and third other fixed contacts 4b2 and 4c2; third and fourth other fixed contacts 4c2 and 4d2; fourth and fifth other fixed contacts 4d2 and 4e2; and fifth and sixth other fixed contacts 4e2 and 4f2, respectively, and the five ground fixed contacts 4g2 are connected in common to the ground. The output or detected signals obtained at the one and the other movable contacts 4R and 4L of the change-over switch 4 are supplied through one and other volume controllers 2R and 2L to one and other sound signal amplifiers 3R and 3L, respectively. The output signals from the one and other sound signal amplifiers 3R and 3L are respectively supplied to one and other output terminals 9R and 9L and also to a sound level meter 10. To the output terminal 9R and 9L, there is coupled a jack 11. A stereophonic head phone 5 has one and other or right and left head phones 5R and 5L to which a plug 12 is connected through a lead wire 13 led out from the head phones 5R and 5L. The plug 12 is inserted into the jack 11 when the apparatus is used in practice. The sound level meter 10 has one and other level displays R and L, each being made of, for example, a number of photo diodes arranged in bar-shape to which the output signals from the sound signal amplifiers 3R and 3L are supplied, respectively. In the embodiment shown in FIG. 1, there is provided a power supply source, for example, battery 14 to apply an electric power through a power supply switch 15 to the sound signal amplifiers 3R and 3L and to the sound level meter 10 and so on. Next, the operation of the embodiment shown in FIG. 1 according to the present invention will be explained. First, the vibration sensors 1a, 1b, 1c and 1d are respectively attached to portions, for example, a bonnet of a motorcar or the like which means that sound or abnormal sound emitted from the engine or the like of the motorcar, for example, is desired to be detected or inspected (see FIG. 7). Then, the power supply switch 15 is turned on, and the head phones 5R and 5L of the stereophonic head phone 5 are respectively connected to the output terminals 9R and 9L or jack 11 through the plug 12. Then, if the change-over switch 4 is manually operated, for example, in such a manner that its one and other movable contacts 4R and 4L are successively connected to the first to fourth one and other fixed contacts 4a1 to 4d1 and 4a2 to 4d2, the same sounds can be successively heard from the one and other head phones 5R and 5L of the stereophonic head phone 5. That is, the sounds emitted from the engine or the like through the bonnet to which the vibration sensors la to 1d are attached, respectively, can be successively and separately heard, and hence whether the engine or the like is normal or abnormal can be inspected or judged successively and separately. In this case, since the output signals from the sound signal amplifiers 3R and 3L are also supplied to the sound level meter 10 or its level displays R and L, respectively, the sound level meter 10, namely its level displays R and L respectively indicate the same levels thereon successively and independently corresponding to the sounds generated at the portions to which the vibration sensors 1a to 1d are attached, respectively. Therefore, the same effect as that in the case of using the stereophonic head phone 5 can be made in a visual manner by watching the sound level meter 10. Also, when the change-over switch 4 is manually switched such that its movable contacts 4R and 4L are connected at the same time to the fifth one and other fixed contacts 4e1 and 4e2, respectively, then the detected sound by the vibration sensor 1a can be heard from the one head phone 5R, while at the same the detected sound by the vibration sensor lb can be heard from the other head phone 5L. Therefore, a source from which, for example, an abnormal sound is emitted can be easily detected. Further, both the sounds can be compared so that the compared result can be used to make various judgements effectively. In this case, since the output signals from the sound signal amplifiers 3R and 3L are also supplied to the sound level meter 10 or its level displays R and L, respectively, the levels corresponding to the sounds respectively detected by the vibration sensors 1a and 1b can be separately displayed on the level displays R and L of the sound level meter 10 at the same time. Thus, the same effect as in the case of using the stereophonic head phone 5 can be effected in a visual manner by using the sound level meter 10. Further, when the change-over switch 4 is manually switched such that its movable contacts 4R and 4L are connected at the same time to the sixth one and other fixed contacts 4f1 and 4f2, respectively, then the detected sound by the vibration sensor 1c can be heard from the one head phone 5R, while at the same the detected sound by the vibration sensor 1d can be heard from the other head phone 5L. Therefore, similar to the case mentioned just above, a source from which an abnormal sound is emitted can be easily detected. Further, both the sounds can be compared so that the compared result can be used to make various judgements effectively. In this case, since the output signals from the sound signal amplifiers 3R and 3L are also supplied to the sound level meter 10 or its level displays R and L, respectively, the levels corresponding to the sounds respectively detected by the vibration sensors 1c and 1d can be separately displayed on the level displays R and L of the sound level meter 10 at the same time. Thus, the same effect as in the case of using the stereophonic head phone 5 can be effected in a visual manner by using the sound level meter 10. FIG. 2 shows an example of an attaching device for attaching each of the vibration sensors 1a to 1d to a portion to be inspected. Although FIG. 2 shows the attaching device for only the vibration sensor 1a, this attaching device can be used, as it is, for each of the other vibration sensors 1b, 1c and 1d. In FIG. 2, reference numeral 6 designates a clip made of such a material to transmit a sound, for example, plastics. For example, the vibration sensor 1a is fixed to one leg 6a of the clip 6 and a magnet 7 is fixed to the other leg 6b of the clip 6. The vibration sensor 1a is attached by the clip 6 or magnet 7 to a portion an abnormal sound or a sound generated at which is to be detected or inspected. In FIG. 2, reference numeral 6c designates the lead wire led out from the vibration sensor 1a. FIG. 3 shows a second example of the attaching device for the vibration sensor. In this example, a suction disk or adapter 8 is attached to the clip 6. The second example of the attaching device is useful when the vibration sensor 1a is attached to a flat plane such as the flat surface of a glass plate or the like because the suction disk 8 can be easily attached by suction to the flat plane. FIG. 4 shows a third embodiment of the attaching device for the vibration sensor 1a. This third embodiment comprises a test bar 9 of a small diameter which is attached to the clip 6. The test bar 9 is made of a material, which effectively transmits a sound, for example, metal, plastics or the like. In FIG. 4, reference numeral 6d is a knob. The third embodiment of the attaching device is useful when a narrow portion, for example, engine, relay or the like is to be inspected. That is, the test bar 9 is inserted into the narrow portion and a sound generated therein is transmitted to the vibration sensor 1a through the test bar 9 and so on. It is also possible that a vibration sensor is directly coupled to a magnet and then the vibration sensor is attached to a portion to be inspected by means of the magnet. It is further possible that a vibration sensor is protected by, for example, a pad and then the vibration sensor is attached to a portion, for example, spring to be inspected by a tape, for example, a magic tape or the like. FIG. 5 shows a practical example of each of the vibration sensors 1a to 1d. Since each of the vibration sensors 1a to 1d is substantially same in structure, only the vibration sensor 1a is described with reference to FIG. 5. In this example, the vibration sensor 1a is directly coupled to the magnet 7 by way of example. In FIG. 5, the lead wire 6c led out from the vibration sensor 1a comprises a plug 1aP at its free end. In FIG. 1, the vibration sensors 1a, 1b, 1c and 1d are respectively connected to input terminals 4A, 4B, 4C and 4D which are respectively led out from the one fixed contacts 4a1, 4b1, 4c1 and 4d1 of the change-over switch 4, but when the vibration sensors 1a to 1d shown in FIG. 5 are employed, the input terminals 4A to 4D are replaced with jacks 4A1, 4B1, 4C1 and 4D1, which will be described later, and the plugs 1aP, 1bP, 1cP and 1dP of the vibration sensors 1a to 1d are inserted into the jacks 4A1 to 4D1, respectively. FIG. 6 shows a main body of a practical example of the abnormal sound detecting apparatus embodying the present invention. In FIG. 6, reference numeral 20 designates a casing made of, for example, plastics. In the casing 20, there are accommodated the parts shown in FIG. 1 except for the vibration sensors 1a to 1d and the stereophonic head phone 5. In FIG. 6, reference numerals 4A1, 4B1, 4C1 and 4D1 denote the jacks which are respectively connected to the one fixed contacts 4a1, 4b1, 4c1 and 4d1 of the change-over switch 4 as described above. Reference numerals 2L1 and 2R1 designate knobs of the volume controllers 2L and 2R, respectively, and 4K is an operation knob of the change-over switch 4. Reference numerals 4AP, 4BP, 4CP and 4DP indicate position marks which correspond to the one fixed contacts 4al, 4b1, 4c1 and 4d1 or 4a2, 4b2, 4c2 and 4d2, respectively. In FIG. 6, reference numerals F1 and F2 correspond to the fixed contacts 4e1, 4e2 and 4f1, 4f2, respectively, and 21 represents a jack to which a recorder, not shown, is connected, when it is desired to record the inspection results. As described above, a sound, especially abnormal sound and its emitting source can be easily and accurately detected by a relatively simple arrangement.

Claims: An abnormal sound detecting apparatus comprising: at least two acoustoelectric conversion means (1a,1b), each for converting an acoustic pressure into a respective electrical signal; first amplifying means (3R) for amplifying the electrical signals from said acoustoelectric conversion means (1a,1b); first volume control means (2R) for controlling the electrical signals from said acoustoelectric conversion means (1a,1b) ; change-over switching means (4) for changeably supplying the electrical signals from said acoustoelectric conversion means (1a,1b) to said first amplifying means (3R) and said first volume control means (2R); and monitoring means (5; 10) responsive to output signals from said first amplifying means (3R); characterised by: second amplifying means (3L); and second volume control means (2L); wherein said change-over switching means (4) is operable to supply changeably the electrical signals from said at least two acoustoelectric conversion means (1a, 1b) to said first and second amplifying means (3R, 3L) and to said first and second volume control means (2R, 2L), and wherein said monitoring means (5; 10) is responsive to output signals from both said first and second amplifying means (3R, 3L). Apparatus according to claim 1, wherein said monitoring means comprises a stereophonic headphone (5) for receiving the output signals from said first and second amplifying means (3R, 3L) to convert the output signals to respective sounds. Apparatus according to claim 1 or claim 2, wherein said monitoring means comprises a sound level meter (10) for receiving the output signals from said first and second amplifying means (3R, 3L) to display the output signal levels. Apparatus according to claim 2, comprising a jack (11) to which the outputs from said first and second amplifying means (3R, 3L) are connected and said stereophonic headphone (5) has a plug (12) which can be inserted into said jack (11). Apparatus according to any one of the preceding claims, comprising attaching means (6) for attaching said acoustoelectric conversion means (1a) to a portion to be inspected. Apparatus according to claim 5, wherein said attaching means comprises a magnet (7). Apparatus according to claim 5, wherein said attaching means comprises a clip (6). Apparatus according to claim 7, wherein said clip comprises a suction disk (8). Apparatus according to claim 7, wherein said clip comprises a test bar (9) fixed thereto. Apparatus according to any one of the preceding claims, wherein said change-over switching means (4) has first and second fixed contacts (4al, 4a2) connected in common, and first and second movable contacts (4R, 4L), said acoustoelectric conversion means (la) being connected to one of said fixed contacts (4al, 4a2), said movable contacts (4R, 4L) being connected to said first and second amplifying means (3R, 3L) via said first and second volume control means (2R, 2L), respectively. Apparatus according to any one of the preceding claims, wherein said change-over switching means (4) has respective pairs of first and second fixed contacts (4al, 4a2; 4bl, 4b2) each pair of which are connected in common, and first and second movable contacts (4R, 4L), each of said at least two acoustoelectric conversion means (1a, 1b) being connected to one of a respective pair of said fixed contacts (4al, 4a2; 4bl, 4b2) of said change-over switching means (4), respectively, said movable contacts (4R, 4L) being changeably connected to respective fixed contacts of said change-over switching means (4) and fixedly connected to said first and second amplifying means (3R, 3L) via said first and second volume control means (2R, 2L), respectively. Apparatus according to any one of the preceding claims, wherein each acoustoelectric conversion means (la) comprises a plug (1aP) and said change-over switching means (4) is connected to a jack (4A1), said plug (laP) being insertable in said jack (4A1).

Inventors: ISHIMOTO SUSUMU, ISHIMOTO, SUSUMU
Applicants: AUTO KONIG
Application year: 1993
Main classification: G01M15
IPC codes: G01M15, G01H1, G01M17, G01M13, G01H17