US2486890A

US2486890A - Decibeloscope

Info

Publication number: US2486890A
Application number: US672222A
Authority: US
Inventors: Rudolph W Stanmyre
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-05-25
Filing date: 1946-05-25
Publication date: 1949-11-01
Anticipated expiration: 1966-11-01

Description

NW. TL, R949 R. w. STANMYRE 2,486,890

DECIBELOSCOPE Filed May 25, 1946 2 Sheets-Sheet 1 INVENTOR. UDOLPH-W TANMY E F a s: 1 R 5 PHTORNEYS Nov. 1, 1949 R. w. STANMYRE DECIBELOSCOPE 2 Sheets-Sheet 2 Filed May 25, 1946 INVENTOR.

RUDOLPH-W STANMYRE /QoMQ/ZZW/ ATTORNEYS Patented Nov. 1, 1949 UNITED STATES PATENT OFFICE Application May 25, 1946, Serial No. 672,222 1 Claim. (Cl. 117411) This invention has to do with a device for visually indicating the volume or intensity, of sound, and which I refer to as a declbeloscope.

The invention, has as an object, a device which is operable to give a clear visual indication of the volume of sounds, and which embodies a structure which is economical to manufacture and which is particularly simple and convenient to operate.

The device has many uses such, for example,

as continuously indicating to a student of elocutlon, or a speaker, the volume, or intensity, of his voice. In this respect, it is particularly helpin] to deaf persons who have extremely great difficulty in properly controlling the volume of their speech.

The invention consists in the novelfeatures and in the combinations and constructions hereinafter set forth and claimed.

In describing this invention, reference is made to the accompanying drawings in which likecharacters designate corresponding parts in all the views.

Figure l is a front, elevational view of a device embodying my invention.

Figure 2 is a schematic wiring diagram illustrating the arrangement and connection of the various elements of the device.

The device consists generally of a series of incandescent lamps, a microphone into which the sound waves are directed, and means connected in circuit with the microphone, and operable to energize the incandescent lamps progressively from one end of the series toward the opposite end thereof, as the volume of the sound, directed into the microphone, increases or decreases. That is, as the volume of the sound increases, the incandescent lamps are lighted progressively, whereupon anyone within visual range of the device is informed as to the volume of the sound.

Preferably, the device is constructed in the form of a cabinet it. The microphone ll may be attached in, or to, the cabinet, or located at any suitable place, or the microphone of a public address system, or the like. may be used. The series of incandescent lamps l2 to 23 are arranged preferably in a vertically extending row in the front wall of the cabinet. A lead 25 is provided for connecting the device to an ordinary convenience outlet. With this arrangement, the device is compact and self-contained, and the only connection necessary to be made is to the power supply by plugging in the lead 25.

As previously stated, the device includes mechanism for progressively connecting the incandescent lamps l2-23 to the power supply. That is, each lamp is energized by a sound intensity, one or more decibels higher than the one below it. As illustrated in the drawings, this is brought about by the use of a thyratron tube 21 associated with each of the incandescent lamps. The common side of the lead 25 is connected to-a fuse 28, and the hot side to a main operating switch 29; This switch is connected to a wire 30 which, in turn, is connected to one side of all the incandescent lamps through wire 3|. The opposite side of each of the lamps is connected to the plate 33 of the respective tubes 21. The cathodes 34 of the tubes 21 are connected to the wire'35, and to the fuse 28 through

wires

36, 31.

The thyratron tubes 21 act in the nature of switches to connect and disconnect the lamps I2 to 23, respectively, to the power supply. The tubes are caused to so function by amplifying the output signal of the microphone it through a three stage amplifier including the amplifying

tubes

38, 39 and 40. The output of the final stage is rectified by the tube M, one side of this tube being connected to a wire 82, through wire it, and the opposite side of the tube is connected to a. wire 4t, through wire 45. A series of voltage dividers 46 are connected across the wires 42, (it, and the movable contacts 48 thereof are connected respectively to the grids 49 of the tubes H.

The voltage divider 46, connected to the grid of tube 21 controlling the incandescent lamp positioned at one end of the-series of lamps, such as the lamp l2 at the bottom of the row, is adjusted so that the full voltage, or nearly full voltage.

impressed upon the

wires

42, 44, is applied to the grid of that tube 21, and the movable contacts of the other dividers are adjusted so that the voltage applied to the grids 49 of the tubes 21 is progressively reduced so that the grid voltage of the thyratron controlling the top lamp 23 is the least.

50 lighted progressively from the bottom to the top.

The device is provided with a power supply transformer 50 having taps 5i to supply current to the heaters of the amplifying

tubes

38, 39, 40, and rectifying tube 4|, a winding 52 to supply 55 filament current to a rectifier 53. and a winding 3 it for one side it of the D. C. amplifier supply A transformer to is also provided toenergiae the heaters of the tubes 21 by the secondary leads 6 I.

The circuit and arrangement of the amplifying unit, including the

tubes

38, 38, 40, is of conventional design and it is not believed necessary to explain that portion of the circuit in detail. Attention is called to the variable gaincontrol -63 connected in the plate circuit of the amplifying tube 38.

The function of the variable gain control 83 is to initially adjust the device for proper operation in any particular situation. For example, if the device is being used to inform a speaker as to the volume of his voice in a small room, the gain control 63 is adjusted so that the series of lamps 12-23 will properly indicate the range of volume for that situation. That is, the gain control would be adjusted to reduce the current supplied to the second amplifying tube 39. If the device, on the other hand, is being so used in a large hall, or auditorium, where the microphone is located a greater distance from the speaker, the gain control is adjusted to increase the current to the second stage of amplification and accordingly, that which is impressed upon the line 42-44. There are also instances where it is desirable to initially adjust the gain control to make the device less sensitive, in order to eliminate the influence of outside sounds, such as street noises, etc.

The voltage dividers 46 are adjusted so that each of the lamps 12-23 will be illuminated progressively by an increase in sound volume, or intensity, of one or more decibels higher than the one below it. I have found that when the device is used as a volume indicator for speech, the setting of the voltage dividers in steps of two decibels is satisfactory. Accordingly, when sound of a given volume is directed into the microphone II, and the gain control 63 is properly adjusted, the lowermost lamp l2 will be energized through the tube 21 which is tripped by the positive voltage produced by the rectifier tube H, as previously explained. Each increase of two'decibels in the volume of the sound, the tubes 21 will be successively and progressively tripped and accordingly, the lamps 12-24 will likewise be progressively energized and with a sound of given volume, all of the lamps will be simultaneously energized up to and including the lamp controlled by the tube 21 tripped by the voltage impressed thereon by that sound signal, and it will be apparent that if the volume of sound is decreased, the indicating lamps will be progressively deenergized, whereby the lamps are progressively energized and deenergized directly in proportion to the rise and fall of the volume of the sound directed into the microphone.

It will be observed that since the tubes 21 have alternating current supply in their plate circuits, they are automatically and substantially instantaneously restored to a non-conducting condition when the grid excitation is removed. When the device is used to indicate sound volume which fluctuates rapidly, such as speech, the duration of the peak of the sound intensity is rather short for proper visual indication. This duration may be varied by selecting one of a plurality of condensers, such as It, H, II, shunted across the output of the rectifying tube 4|. These condensers are of different capacity, and the greater the capacity, the greater the damping effect. The condensers are selectively connected in a circuit by a movable contact 13 which is operated by a knob Ii arranged on the face of the cabinet It.

A dial 16 is provided to indicate the condenser selected. Preferably, the condenser of greatest capacity has a capacity which will provide a time factor of about one and one-half seconds. With this time lag, the device disregards peaks entirely and reads mean values. The condenser of least capacity is such as to provide a substantially instantaneous indication, and the intermediate condenser, or condensers having capacity somewhere between the end condensers of high and low capacity.

The variable contact of the adjustable gain control 63 is operated by a knob 11 also available on the face of the cabinet, and a dial I8 is provided to indicate the setting of the contact. Preferably, the dial it is graduated so that the movable contact of the gain control can be adjusted in steps equivalent to two decibels each. It has been found that this arrangement gives an effective adjustment for the device when it is used for a voice volume indicator. However, it is apparent that adjustments of any magnitude can be effected for any particular use to which the device may be put.

Sufiicient bias is taken from the

amplifier power supply

55, 56, and applied to the grids of the tubes 21 to make certain that the tubes will be normally non-conducting. A load resistor is provided with a movable contact 8| connected to the ground support 36. By adjusting the movable contact 8!, the negative bias to the tubes 21 can be adjusted so that the tubes cut oil sharply when no current is supplied to the grids of the tubes from the

circuit

42, 44. This adjustment is in the nature of an initial adjustment made when the tubes 21 are installed, or when any one or more of the tubes are replaced, as will be well understood by those familiar with the art.

What I claim is:

A decibeloscope for visually indicating sound volum comprising a plurality of electric lamps arranged in a vertical row, a power supply for energizing said lamps, a microphone, inertia free means connected in circuit with said microphone and operable to progressively connect said lamps to said power supply in proportion to the volume of the sound directed into said microphone, and means adjustable to control the duration said respective lamps are connected to the power supply after the sound volume has decreased.

RUDOLPH W. STANMYRE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,120,971 Bailey June 21, 1938 2,179,101 Read, Jr Nov. 7, 1939 2,331,236 Schaefer Oct. 5, 1943 2,398,046 Schaefer Apr. 9, 1946 2,407,286 Kinkead Sept. 10, 1946