US 3328524 A
Description (OCR text may contain errors)
June 27, 1967 G. R. BECHTEL ETAL 3,
SOUND SYSTEM FOR BANKING SERVICE EQUIPMENT 3 Sheets-Sheet 1 Filed Nov. 14, 1963 INVENTORS Geo ekBeah/fieamz BY Newbon J- m We: W
ATTORNEYS June 27, 1967 Filed Nov. 14, 1963 G. R. BECHTEL ETAL SOUND SYSTEM FOR BANKING SERVICE EQUIPMENT 3 Sheets-Sheet 2 26 I' i I 25 27 i i X? i 27 Zkl 2|' I Q i Q 2 I 27 L i 'l/ 24 k I 23 i I a 1 e DJI: :[G
Fig.4 ED: AMPLIFIER :fl3 s s 3 so a o 5 TIME 30 a +05 INVENTORS GeorgeRBedzMm ATTORNEYS FREQUENCY IN CPS FREQUENCY IN CPS June 27, 1967 G. R. BECHTEL ETAL 3,328,524
SOUND SYSTEM FOR BANKING SERVICE EQUIPMENT Filed Nov. 14, 1963 3 Sheets-Sheet 3000 NO SUPPRESSORS 3600 SUPPRESSORS ON SPEAKERS 3400 AND OUTSIDE MIKE 3200 SUPPRESSORS ON SPEAKERS 3000 SUPPRESSOR ON OUTSIDE 2800 MIKE&SPACED FROM WALL 2600 2400 2200 2000 I800 I600 I400 I200 I000 800 600 400 200 SUPPRESSOR ON OUTSIDE MIKEAI AGAINST WALL 6 MAXIMUM DB BEFORE FEEDBACK-INSIDE MIKE NO SUPPRESSORS SUPPRESSORS ON SPEAKERS AND OUTSIDE MIKE SUPPRESSORS ON SPEAKERS SUPPRESSOR ON OUTSIDE MIKE81SPACED FROM WALL SUPPRESSOR ON OUTSIDE MIKEBIAGAINST WALL MAXIMUM D8 BEFORE FEEDBACK-OUTSIDE MIKE INVENTORS Geg$qeR.Bec]d@LM 7 BY ewlmmllfny Fm, w mwm ATTORNEYS United States Patent 3,328,524 SOUND SYSTEM FOR BANKING SERVICE EQUIPMENT George R. Bechtel and Newton J. Krug, Canton, Ohio,
assignors to Diebold, Incorporated, Canton, Ohio, a
corporation of Ohio Filed Nov. 14, 1963, Ser. No. 323,733 3 Claims. (Cl. 179-1) ABSTRACT OF THE DISCLOSURE An arrangement of microphones and speaker in banking service equipment for voice communication between a teller inside and a customer outside a sound-barrier building wall wherein the customers microphone is mounted in a sound-absorbing box located behind and mounted against the wall, with the microphone directed toward the customer through an opening in the wall to reduce feedback and permit increased sound system volume.
This invention relates to an improved sound reproduction system for banking service equipment used for the convenience of bank customers, and more particularly it pertains to a sound reproduction system for eliminating or minimizing feedback.
Banking service equipment includes such devices as walk-up windows, drive-up windows, and so-called television banking stations, Which are placed at strategic locations for the convenience of bank customers. Such equipment usually includes a customers station and a tellers station separated from each other so that direct two-way oralcommunication between the customer and the teller is not feasible.
For various reasons prior sound reproduction systems for banking service equipment have not been satisfactory. Under normal conditions a system may be set for a suitable volume for both incoming and outgoing speakers. Due to distractions of outside noises, such as during traffic hours, it is necessary for a bank teller in a drive-up window to frequently adjust the volume. Feedback usually develops and it becomes necessary to immediately reduce the volume below an audible level. For that reason most prior audio systems have been inadequate.
Feedback i high frequency distortion caused by sounds of a speaker picked up by a microphone. It is a sustained oscillation or howling and is caused by the return of sound waves from the speaker to the microphone in the same sound system and causing reinforcement of the output. The type of feedback involved here is external of an amplifier. Feedback normally occurs because the microphone is too near the speaker or the sound from the speaker is directed substantially toward the microphone. Feedback is most prevalent where two basic channels or audio systems are operating simultaneously. Where sound systems having dual channel amplifiers with two microphones and two speakers are operating, it is difiicult to get good audio quality. Inasmuch as an audio system for a drive-up window merely involves the transfer of voices between two people on the opposite sides of a glass window (sound barrier), a system with the basic components of an amplifier, mikes, and speakers should suffice. Such a basic system is conducive to the problem of feedback, which problem can sometimes be corrected by the provision of a more complicated amplifier having builtin components for permitting the increase of volume without development of feedback.
In relation to regeneration and oscillation, feedback can occur in a single stage of an amplifier or it may appear as over-all feedback through several stages that are 3,328,524 Patented June 27, 1967 "Ice operating on the same frequency. Feedback may be reduced by isolation of the various components of the amplifier, as well as good shielding of tuning capacitors and coils. Feedback is not as prevalent at low frequencies as it is at higher ones.
Over-all feedback in a multistage amplifier is avoided by first filtering the output circuit before running it back near the input circuit. However, the amplifiers used in bank windows are unusual in that they are two-channel units as compared to the single channel standard amplifier. While all the above conditions have been met, feedback is still quite apparent in these amplifiers because there is cross channel as well as single channel feedback. Also, any stray sound flowing through the window will cause a mechanical feedback. The more complicated sound systems, however, are not only more costly, but much more difficult to adjust and maintain, and their use for mere transfer in a dual channel system for drive-up windows is not always justified.
It has been found that the problem of feedback can be substantially eliminated or minimized at the usual audio levels used in banking service equipment by the provision of a relatively inexpensive bafiie box or suppressor for producing a directional effect upon sound entering the outside microphone. It is not suitable for the inside or teller microphone or speaker. By providing the outside or customers microphone with the sound baffle, suflicient sound waves are filtered out to suppress feedback which normally occurs when the volume of the system is increased to overcome extraneous trafiic noises. However, if the inside microphone and/or speakers areprovided with similar bafi'les, some of the desired sound waves are filtered out which are otherwise necessary for high gain with no feedback which avoids clarity.
With prior systems the sounds treated acoustically after amplification produced some undesired sounds and resulted in feedback at lower volume levels. With the device of the present invention the tones are partially absorbed and partially reflected prior to amplification by striking the barrier wall before entering the microphone.
Accordingly, it is a general object of the present invention to provide a sound system for banking service equipment having means for directing partially absorbing and partially reflecting sound waves entering the outside microphone.
It is another object of this invention to provide a sound system for banking service equipment which eliminates stray sounds caused by sound waves which bypass the outside microphone and would, therefore, cause mechanical feedback at lower volume levels.
It is another object of this invention to provide a sound system for banking service equipment in which a dual amplifier provides a microphone and speaker on each side of a ound barrier and which equipment filters out unwanted sound waves for eliminating feedback at lower volume levels. I
It is another object of this invention to provide a sound system for banking service equipment which directs the sound waves prior to amplification so that the waves strike a barrier wall before entering the outside microphone.
Finally, it is an object of this invention to provide a sound ystem for banking service equipment which is economical to manufacture, easy to operate, and requires a minimum amount of maintenance and repair.
These and other objects and advantages apparent to those skilled in the art from the following description and claims may be obtained, the stated results achieved, and the described difiiculties and problems overcome and solved by the parts, elements, constructions, mechanisms, combinations, subcombinations, and arrangements, which comprise the present invention, the nature of which is set forth in the following general statement, preferred embodiments of whichillustrative of the best mode in which applicants have contemplated applying the principles-are set forth in the following description and shown in the drawings, and which are particularly and distinctly pointed out and set forth in the appended claims forming part hereof.-
Generally the present invention may be described as comprising banking service equipment having a customers station and a tellers station beyond direct oral communication with the customers station, audio means for providing indirect communication between the stations, said means including a bank tellers microphone and a speaker as well as a customers microphone and a speaker, the customers microphone being enclosed in a box-like sound barrier having opposite side, top, bottom, and rear side walls, said side and top and bottom'walls providing an opening on the side of the microphone opposite the rear side wall, the microphone being disposed against the rear side wall and facing said opening, the walls being composed of acoustical material,v whereby some sound waves strike and are partially absorbed and partially reflected by the box-like walls before entering the microphone.
In the drawings:
FIGURE 1 is an elevational view of a bank drive-up window;
FIG. 2 is a vertical sectional view taken on the line 22 of FIG. 1;
FIG. 3 is an enlarged sectional view through the outside microphone assembly;
FIG. 4 is a diagrammatic view of a dual channel audio system of the type involved herein;
FIG. 5 is a decibel-frequency chart;
FIG. 6 is a graph showing variations of maximum decibels at varying frequencies for the inside microphone for different combinations of suppressors on speakers and microphones; and
FIG. 7 is a graph showing variations of maximum decibels at varying frequencies for the outside microphone for different combinations of suppressors on speakers and microphones.
A drive-up window is generally indicated at 1 in FIGS. 1 and 2 and isusually built in a building wall 2. The windowl includes upper and lower portions 3 and 4, the former of which is composed primarily of bullet-proof glass panels, and the latter of which is preferably composed of metal walls. An audio system is also provided which includes an inside (tellers) microphone 5, an outside (customers) microphone 6, and an inside speaker 7 and an outside speaker 8. A tellers drawer 9 is provided within the lower portion walls which moves into and compartment 13 with walls 14 and 15. The upper wall 14 includes a front wall 16 as well as an inturned wall 17.
Conversation between the teller and the occupant of the automobile 11 is provided by a two-way audio system which includes the microphones 5 and 6, the speakers 7 and 8, and an amplifier 18 (FIG. 4), the latter of which is connected to an outside source of current by lines 19. The speakers 7 and 8 are mounted in an enclosure between the walls 14 and 17, as shown in FIG. 2. The inside microphone 5 preferably depends from the walls 17 and the outside microphone is mounted within the front wall of the lower portion 4 of the window 1 and preferably below the counter 12.
As shown, the inside speaker 7 is directed toward the rear wall 15, and the outside speaker is disposed above and is aligned with an opening 20 in the inturned wall 17 adjacent the front wall 16. Without further modification the foregoing arrangement of the microphone and speakers would operate to provide for two-way communication on either side of the sound barrier, i.e., glass panels 3. However, the foregoing arrangement showing a normal situation is limited in the amount of volume that can be used before feedback occurs.
As shown in FIG. 3 the outside microphone 6 is preferably mounted within a sound baflie box or suppressor 21 which is a rectangular member having two pairs of opposite side walls including opposite walls 22 and 23 and a base wall 24 which faces an opening 25 in the lower portion 4. The box is preferably composed of a soundabsorbent material or acoustical tile such as Celotex. As shown in FIG. 3, the walls 23 and 24 are in abutment at 26 with the inner surface of the lower wall portion 4. Accordingly, all sounds indicated by the lines 27 entering the box 21 are transmitted either directly or indirectly into the outside microphone 6 which faces the opening 25 and on an axis therewith.
Formerly it had been the practice to place the box 21 away from the inner surface of the wall 4 with a space 28 therebetween. With that construction it was found that some of the sound waves 27a entering the opening 25 pass into the spacing 28 between the box 21. and the wall 4. The result of that former arrangement was the development of feedback at a lower volume level of operation of the audio system. 7
To ascertain better audio conditions for banking service equipment, tests were made with the inside and outside speakers as well as the outside microphone enclosed within sound suppressors or bafiie boxes 21.'The speakers were enclosed in boxes similar to the boxes disclosed in Patent No. 3,301,956. Results of the several tests are set forth in the table below in which the maximum volume readings at the lower edge of feedback are listed for the various frequencies and the human voice.
MAXIMUM VOLUME READINGS AT LOWER ED GE OF FEEDBACK IN DECIBELS Test Frequencies No Baflie Box Baflle Box Only on Boxes on Speakers and Box Only on Mike Box Only on Mike at Speakers Out e Spaced From Wall Wall In Mike Out. Mike In Mike Out Mike In Mike Out Mike In Mike Out Mike In Mike Out Mike out of the window through doors 10 for the convenience The decibel values listed are the maximum volumes of a bank customer seated in an automobile 11. The drive-up window 1 is also provided with a work surface or counter 12 which extends across and over the drawer 9 in a conventional manner. The window 1 forms a tellers obtainable for each frequency or voice before feedback occurs. For all readings a decibel meter was located at the approximate position of the customer or teller. When reading decibels for the inside mike, a meter was located at the approximate position of the customer in an automobile near the outside speaker. For taking readings of the outside microphone, a decibel meter was located at a position corresponding to that of the head of a teller near the inside speaker. The values for the outside microphone are lower than those for the inside mike because the sounds tested travel through outside air without the benefit of walls such as the inside walls enclosing the inside microphone.
Test N0. 1 involved a standard audio system without suppressors on either speaker or microphone. The values for the inside microphone are the sound levels observed from the outside speaker. Likewise, the values for the outside microphone are the sound levels observed from the inside speaker.
Test No. 2 involved an audio system with the speakers only enclosed within suppressors. Higher volumes are attained before feedback than for corresponding frequencies in Test No. 1.
Test No. 3 involved the use of suppressors on both speakers and the outside microphone only. The suppressor on the microphone was placed against the inside surface of the lower wall portion 14 as shown in FIG. 3 of the drawings.
Test No. 4 involved the use of a suppressor on the outside microphone only in the position shown in the broken line of FIG. 3 of the drawings. In that position the front end of the baffle box or suppressor 21 is spaced from the inner surface of the front wall panel 4 by approximately 1 so that some of the sound waves enter the interior of the drive-up window through the spacing, causing feedback at a lower volume.
Test No. 5 involved the use of a suppressor on the outside microphone only as shown in FIG. 3 of the drawings. Suppressors for the inside and outside speakers 7 and 8 were removed, as for Test No. 4. The front end of the suppressor or bafiie box 21 was against the inner surface of the wall 4 leaving no spacing through which some sound waves entered as for the conditions of Test No. 4. The volume readings for Test No. 5 are substantially greater than those for all prior testing conditions and particularly for Test No. 4. That is, the maximum volumes before feedback for both frequency and voice tests were obtained when the outside microphone only was enclosed within a suppressor box.
The data listed in the table are graphically illustrated. In FIG. 6 the curves show readings taken at the outside speaker for testing the inside microphone. It was found that where a suppressor or baffie box is used only on the outside microphone with the open end of the box in contact with, rather than spaced from the inner surface of the Wall 4, the maximum volume before feedback could be obtained. Indeed, where the open end of the suppressor is spaced from the wall 4, the maximum volume obtained in the system is considerably less. The same is true for other combinations of suppressors such as (1) on the speakers and the outside microphone or (2) only on the speakers.
In FIG. 7 the readings were taken at the inside speaker for testing the outside microphone and the highest volumes were obtained with one suppressor only on the outside microphone with the open end in contact with, rather than spaced from, the inner surface of the wall 4. With other tested combinations wherein suppressors were used (1) only on the inside and outside speakers or (2) on the speakers and the outside microphone, lower volumes were obtained before feedback developed.
FIGS. 6 and 7 graphs show that the greatest possible gain without feedback occurs when a suppressor is mounted on the outside microphone only. Theoretically the maximum possible voice gain in the inside microphone is 106 decibels for a single channel (FIG. 6). With the suppressor on the outside microphone the gain is 98 decibels. The amplifier efiiciency on the channel, therefore, is 92.5% (98 divided by 106). Similarly, the maximum possible theoretical voice gain on the outside microphone is 104 decibels on a single channel. With a suppressor on the outside microphone the gain is decibels. The amplifier on this channel, therefore, is 91.5% eflicient (95 divided by 104).
The foregoing maximum 104 and 106 decibels are for a given amplifier used in these experiments with a given wattage and the results would be proportional in any other system as related to its rated power.
Assuming an average maximum voice gain of 105 decibels, the amplifier on the setup for the inside microphone is 93.5% eflicient. Therefore, the amplifier for the setup of FIG. 7 on the outside microphone is 90.5% eflicient.
' One explanation of the foregoing results may be shown in FIG. 5 in which a sound wave is graphically illustrated. The curve represents the optimum volumes achieved by the use of a bafile box or suppressor 21 with the open end in contact with the inner surface of the wall 4. When the box 21 is spaced from the wall 4 so as to permit some sound waves 27a to pass into the space indicated by the arrow 28 in FIG. 3, the maximum volume obtained before feedback is reduced. The resutling maximum volume lies between the shaded areas 29 in the peaks and valleys of the sound curve in FIG. 5. If baflle boxes or suppressors are also added to the inside and outside speakers 7 and 8, the greatest volume achieved before feedback by the system is reduced by the shaded areas 30, leaving a maximum volume obtainable which is unsatisfactory for operating conditions where outside noises, such as traflic, normally prevail.
The device of the present invention discloses that more volume can be obtained from presently existing sound systems in bank service equipment when the outside microphone is enclosed within a baflle box or suppressor with the open end of the box in contact with the outer front wall of the equipment such as a drive-up window. j It has also been found that where the open end of the bafiie box or suppressor is spaced inwardly from the wall so as to permit some of the incoming sound waves to bypass the outside microphone, said sound waves prevent the optimum development of volume before feedback, which volume would be completely satisfactory for normal operation of the sound system.
Moreover, it has been found that where baflie boxes or suppressors are also added to the inside and outside speakers, the maximum volume obtained is less than satisfactory in some given instances, even where a baflle box or suppressor is also provided for the outside microphone.
In the foregoing description certain terms have been used for brevity, clearness and understanding, but no unnecessary limitations are to be implied therefrom as such words are used for descriptive purposes and are intended to be broadly construed.
Moreover, the embodiments of the improved construction illustrated and described herein are by way of example aud the scope of the present invention is not limited to the exact construction shown.
Having now described the invention, construction, operation and use of preferred embodiments thereof and the advantageous new and useful results obtained thereby; the new and useful sound system for banking service equipment and reasonable mechanical equivalents thereof obvious to those skilled in the art are set forth in the appended claims.
What is claimed is:
1. In banking service equipment having a customers station and having walls forming a tellers station beyond direct oral communication with the customers station, the walls including a sound-barrier wall having inner and outer surfaces with the outer wall surface adjacent the customers station; audio means for providing indirect communication between the stations and including a tellers microphone and a speaker at the tellers station and a custornrs microphone and a speaker at the customers station; the combination therewith of feedback suppression means, said feedback suppression means including box-like walls forming an acoustical chamber having an open end, said barrier wall being formed with an opening, the box-like walls being mounted in abutment with the barrier wall inner surface and'with the chamber open end aligned with the barrier wall opening, and the customers microphone being mounted within said acoustical chamber.
2. The construction set forth in claim 1 in which the box-like walls form a generally rectangular baffle box having five walls forming pairs of opposite side walls and one end wall, the opposite side walls having end portions forming the acoustical chamber open end opposite said end 1 wall, and the side wall end portions abutting the barrier wall inner surface around the barrier wall opening.
3, The construction set .forth in claim 2 in which the bafile box walls are formed of sound-absorbent acoustical material.
References Cited UNITED STATES PATENTS 1,969,704 8/1934 DAlton 179-1 2,177,769 10/1939 Erickson 1791 KATHLEEN H. CLAFFY, Primary Examiner.
R. P. TAYLOR, Assistant Examiner.