US3558822A

US3558822A - Locator

Info

Publication number: US3558822A
Application number: US731039A
Authority: US
Inventors: Stephen L Moshier; William B Van Lennep; Edmund G Perry
Original assignee: Listening Inc
Current assignee: Listening Inc
Priority date: 1968-05-22
Filing date: 1968-05-22
Publication date: 1971-01-26
Anticipated expiration: 1988-01-26

Abstract

MY DISCLOSURE IS OF A DEVICE FOR PROJECTING A BEAM OF HIGH FREQUENCY, STACCATOLIKE, ACOUSTIC PULSES WHICH, WHEN DIRECTED TOWARD A DISTANT OBJECT CAPABLE OF REFLECTING AN ECHO, WILL ENABLE THE USER TO DETERMINE THE DISTANCE AND CHARACTER OF THE OBJECT BY INTERPRETING THE QUALITY OF THE ECHO. THE DEVICE INCLUDES A HOUSING IN WHICH IS CONTAINED A LOUDSPEAKER, AN ELECTRICAL PULSE-GENERATING CIRCUIT CONNECTED TO THE SPEAKER AND A HORN ASSOCIATED WITH THE SPEAKER FOR CONFINING THE ACOUSTIC PULSE IN A DIRECTIONAL BEAM.

Description

United States Patent [72] Inventors Stephen L. Moshier;

William B. Van Lennep; Edmund G. Perry,

Cambridge, Mass. [21] AppLNo. 731,039 [22] Filed May22, 1968 [45] Patented Jan.26, 1971 [73] Assignee Listening Incorporated Arlington, Mass.

a corporation of Massachusetts [54] ACOUSTIC LOCATOR 1 Claim, 2 Drawing Figs.

52 U.S.Cl 179 1,

340 1 51 lnt.Cl G0ls9/46 so FieldofSearch 179 1,

1 MEG; 340/ l [5 6] References Cited UNITED STATES PATENTS 3,337,839 8/1967 Nelkin 340/1 3,412,207 1 1/1968 Sugawara l79/l 3,454,922 7/1969 Dory 340/l Primary ExaminerKathleen Hi Claffy Assistant Examiner-Douglas W. Olms Attorney-Kenway, Jenney and Hildreth ABSTRACT: My disclosure is of a device for projecting a beam of high frequency, staccatolike, acoustic pulses which, when directed toward a distant object capable of reflecting an echo, will enable the user to determine the distance and character of the object by interpreting the quality of the echo. The device includes a housing in which is contained a loudspeaker, an electrical pulse-generating circuit connected to the speaker and a horn associated with the speaker for confining the acoustic pulse in a directional beam.

PATENTEU MG Ian;

INVENTORS' NEP I FIG. 2

TTORNEYS' ACOUSTIC LOCATOR SUMMARY OF THE INVENTION My invention includes a speaker or similar device capable of emitting an acoustic pulse of relatively high frequency and of short duration. The speaker is combined with a horn which serves to confine the acoustic pulse into a beam so that the beam may be directed towards a distant echo-producing object thus enabling the user to serve the presence, distance and character of the distant object by means of its echo. Electrical circuit means are provided to energize the speaker repeatedly and cause it to emit the acoustic pulses. Means are further provided for varying the repetition rate of the outgoing pulses.

My invention may be used in numerous environments among which are as a navigational aid for mariners, blind persons, or in testing the acoustic qualities of a building or other structure. The device may also be useful in an alarm system (security and tire protection), mapping and motion detection in general. It is not necessarily restricted to use in an atmospheric environment but could be used in any medium, such as water, capable of conducting acoustic pulses. When used in water, however, it obviously must be of waterproof construction.

In testing my invention with a number of people, I found that after a relatively short period of practice each of the blindfolded subjects was able to discriminate between the reflected echoes of wooden buildings, automobiles, a fence and an apartment house. The subjects were able to navigate along a sidewalk by reference to the reverberant sounds of buildings and the curb as well as sensing people approaching from a distance of twenty to thirty feet.

Tests were also conducted on a boat and I found that once the tested subject became familiar with the different reflective sounds of objects, such as buoys, channel markers and boats, he was able to give directions to the operator of the boat to guide him through a channel and under a bridge. Shore lines, islands and anchored boats were also distinguished. Tests producing such satisfactory results were conducted with blindfolded test subjects as well as in actual fog and reduced visibility.

My invention will now be described in greater detail with reference to the accompanying drawings wherein:

FIG. 1 is a broken away side elevation of my device; and

FIG. 2 is a schematic of the electrical pulse generating circuit.

As illustrated in FIG. 1, my invention includes a housing having an open forward end. A speaker 12 is mounted within this opening of the housing 10. A bracket 14 is supported within the frame 10 by conventional means and serves to support other elements of the device such as a battery 16 and an electrical circuit 18. A born 19 is provided at the forward open end of the housing 10 to confine the sound emanating from the speaker 12 to form an acoustic beam. I have found that an acoustic beam having a maximum arc width of approximately 60enables the beam to cover a relatively wide area and yet retain its directionality. For example, a horn that is 3 inches long and enlarges from a 3 inch diameter at its rearward end to a 6 inch diameter at its forward end produces a beam having a desirable arc width. The horn 19 may be removably mounted to the housing 10 to enable substitution of a horn of a ditferent configuration which may project a more narrow acoustical beam. Confming the beam to a more narrow width would cause the device to have more sensitive directional characteristics in that the beam would have to be more accurately directed to the acoustic target in order to produce the strongest echo.

The speaker 12 is connected to the output of the electrical circuit 18, which may be of conventional design and is intended to repeatedly generate an electrical pulse of a relatively short duration so that the speaker 12 may emit a series of high frequency staccatolike clicks. The circuit 18 incorporates means to vary the rate at which the pulses are repeated. In use the pulse repetition rate is intended to be adjusted so that when the horn is directed toward a distant object or acoustic target, the echo from a pulse will return to the users ear before the following acoustic pulse is emitted by the speaker. It has been found desirable to vary the pulse repetition rate so that the echo returns approximately midway between outgoing pulses. The pulse repetition rate required to enable the echo to return midway between outgoing pulses provides an indication of the distance between the device and the acoustic target. When the target is close, the echo will be quickly returned and the pulse repetition rate must be increased. When the target is distant, the greater echo return time will require a slower pulse repetition rate.

The electrical pulse-generating circuit is schematically illustrated in FIG. 2 and includes an on-off switch 20 that may be closed to cause current to flow from the battery 16. When the switch 20 is closed, the capacitor C2 is charged. A relaxation oscillator circuit, shown at 24, acts as a triggering circuit for silicon control rectifier 22. When the rectifier 22 is enabled, the charge stored in the capacitor C2 passes through the rectitier 22 and the coil of speaker l2 causing the speaker to emit a click. The relaxation oscillator circuit 24 is of conventional and well-known design. A full explanation of its operation may be had by reference to page I93 of the sixth edition of the Transistor Manual edited and published by General Electric Company, Syracuse, N.Y.

A preferred embodiment of my invention generates an electric pulse having a l0-90 percent rise time lying in the range of 208O microseconds and a relatively long delay time constant in excess of l millisecond. The pulses are generated at a rate that is determined by the setting of a control knob 28 (see FIG. 1) which in turn determines the value of R2 in FIG. 2. A desirable range for the pulse repetition rate is between 0.2 and 200 pulses per second. The pulses may have a peak amplitude of 15 volts into an 8 ohm speaker generating approximately 28 watts of power. This would be typical of a practical unit. Some representative values for the schematic diagram of FIG. 2 are as follows:

Cl O.5 microfarads;

C2 --2.2 microfarads; and V 9-27 volts.

The unijunction transistor 26 may be of the type 2N2646, and the silicon-controlled rectifier may be of the type MCR2305-c0.

The combination of the speaker 12 and horn 18 should preferably have a low frequency cutoff value between 1 and 5 kilocycles in order to produce the desired high frequency staccato clicks. The circuit 18 provides an electrical exciting signal to the speaker 12 which causes the speaker-horn combination to emit an acoustic pulse at its natural resonant frequency. I have found that any acoustic pulse duration of 0.2 milliseconds is about optimum for most of the contemplated uses and hence a resonant frequency of about 2.5 kilocycles is appropriate.

As mentioned above, my device has practical application as a safety device for boat owners during periods of reduced visibility as well as for use for the blind as an oriented device in walking. I have found that with little practice the user will become accustomed to the different echoes produced by various targets. Tests by yachtsmen have demonstrated that the device's useful range exceeds half a mile in air over open water. With little difficulty one may also be able to sense the relative distance of one acoustic target from another. My device may be of simple, lightweight construction and preferably should feel and handle like a flashlight.

The foregoing is intended merely as an illustrative example of my invention and should not be construed as limiting its scope except as set forth in the appended claims. Other embodiments may be constructed without departing from the spirit of my invention. For example, a mechanically operable device could be substituted for the electrical pulse generator.

We claim: 1. Acoustic echo object'locating apparatus, said apparatus comprising:

a loudspeaker having means for confining acoustic energy emitted therefrom to a relatively narrow beam, said loud speaker with said confining means having a natural resonant frequency in the order of 2.5 kilocycles;

means including an electronic oscillator for energizing said loudspeaker with repetitive pulses; each having a duration generally corresponding to said resonant frequency, thereby to cause said speaker to emit a succession of audible acoustic pulses, said oscillator including means for adjusting the pulse repetition rate to permit successive pulses to be timed so that echoes of said pulses returned from an object in the beam path occur midway between transmitted pulses thereby presenting a relatively easily perceived condition to an operator of the apparatus; and housing means for holding said loudspeaker, said energizing means, and a battery for powering said energizing means in a unitary configuration adapted to be hand held; whereby objects may be located by aiming the apparatus to direct said. beam against an object and by adjusting the pulse repetition rate until the operator perceives that echoes from the object occur midway between trans mitted pulses, the pulse rate so determined being indicative of the distance to the object with the aiming of the apparatus being indicative of the direction of the object from the operator.