Document OJqeLDmoVYgGJJ4VnkqQG4BqX

-/';qi .ojnO'ij iftl'jftfcbJh m'n'fa fiircb SO, 196b SU5TBT: NOISE CONTROL To Members or the Lead Industries Association, Inc.: Attached Is the second detailed report of a case history of a successful experimental Installation of lead for noise control. It follows the first case history sent to you with our letter of December U, 1562. Because of the obvious success of the Installation and the 0 satisfaction expressed by the owner, an article ea this Installa tion has been cleared for publication In an early Issue of "Lead," and a brief description was included in on article for "American City Magazine" to be published shortly. In addition, an article on the subject byllned by Detective Allr.cra of the Bergen County, N. J. Prosecutor's Office will soon appesr in the cagazine "Law and Order" which will reach hundreds, and perhaps thousands, of others with a oinllar problem. Eventually reprints of both the "American City" and "Law and Order" articles vlll be cade avail able to members. Ve hope you will find the information contained In this most recent case history useful In your own promotion and sale of lead for noise control. Very truly yours. 'JL-t RLZ:nk Executive Vies President 0 sau. ijimi *]] j i LIA2 4035 v'l-: )i ,5 ~ :;! r.\7 '< = Nad lrt(twttri Ai*<iotiof>, ln<. 293 Maditon Av N*w York 17, N Y. Abend w*th Lend " "1 ,BW HM'-IJ Y_JUWI March 9, 1964 LEAD FOR NOISE CONTROL -- CASE HISTOfi? # 2 Bergen County Polygraph Roes Surgary: In October, 1961, Detective Herbert Alicerj of the Bergen County, N. J., Prosecutor'* Office cane to LIA for advice and help in soundproofing a rocn used for polygraph ("lie detector") test*. His requirements were quite high, and the existing rocn was quite poor in tern* of acoustical privacy and noise level. To further ccspllcate the natter, radical revision of the reco could not be undertaken without authorization under a county budget, incurring Indefinite delay. Thus any alteration had to be in the general category of "minor alteration or additions" rather than "capital Improvement". Approximate measurements of the rods were 9 * 12 x 9 fret high and it was flanked by corridors on two sides, an office on the remaining long side, and an observation roan (with one-way mirror) on the remaining short slue. All walls except the short wall adjacent to a corridor were sheet steel office partitions. The remaining wall was plastered svesenry. A soundproof door had been purchased and Installed before Allmcr* brought this problem to us. Supplying sheet lead, cement, and leaded plastic (for door gasketing), LIA planned and supervised addition of 4-pound sheet lead to all vails. Additional materials (lumber, acoustical tile for Interior finish, glass N 1978.01 nwnpaeew^as t ItWaa LIA24036 aUb `""**^* **ri,>-~------ -* Bergen County Polygraph Boas -2- March 9, 1964 o fiber, hardware) and all labor vera furnlahed by the County. Tha results. tabulated below, were? Boise Reduction (nine-frequency average) before after Improvement Fran hall to polygraph room Fran observation to polygraph roan Fran office to polygraph roan 23.5 db 35 32.5 1*0.5 **1.5 **1 17 db 0.5 11.5 These results arc Impressive and the achieved level of noise reduction la good. The effect, however, van disappointing. The polygraph rooa had become so quiet that the noise leaking Into it, though small, was still quite disturbing. This was remedied by using a fan In the polygraph room. It supplies, in addition to air movement, a masking noise which Is not, itself, objec tionable In any way. This masking noise is so great In comparison to the small amount of external noise leaking In that virtually nothing outside the rooa can be heard. In our tests we employed a noise source in the observation rood which was approximately as Intense as the noise produced by a subway train. The accompanying plotted data show that this noise was not perceptible over the fan noise in the polygraph room. Total materials cost for the Job was $600, of which $h00 was borne by LIA. labor, other than supervisory and texting, was 3 man days by carpenters and painters and la valued at 41000. These results were not achieved easily or directly. Door gasketing, especially, required repeated visits by LIA staff members and the American Smelting and Refining Company R & D people who furnished testing equipment and worked with LIA on the project. Both organizations can say they learned ouch, but the outstanding lesson Is that there Is no single, simple, sure fire way of soundproofing an existing room. -more- 4i > wifw LIA24037 CBS' Bergen Count/ Polygraph Room -3- linrcb 9, IS64 The Bergen County Prosecutor'* Office and Detective Allmers are veil pleased with the roam. They are satisfied that It meet* their acoustical requirements and probably Is much better chan the majority of roooa used for this purpose. Polygraph Ro o d Requirements: Polygraphs are used In police work and have been shown to pay for themselves quickly by saving vast amounts of time In. investigations -- not Infrequently Just when time Is precious. In an examination, the voluntary subject is told exactly what questions vlil be asked ahead of time. He Is then asked these questions and a record of his pulse, breathing pattern, and other responses is made. Qualified polygraph examiners ilka Detective Allmers can analyze such records and -el., whether the subject ha# answered truthfully. Kolse, or ar.y other distraction, can Itself Induce the Involuntary reactions which the polygraph records. Thus, a subject answering "yes" truthfully to a question, might unconsciously react to a sudden noise and Indicate that he was lying or, at least night have been lying. While we are not aware of any published acoustical standards for poly graph rooms. It is evident that the noise level in then should be low enough for conversation at comfortably low levels. Xire important. It Is essential that no distracting noise be allowed to confuse the recorded findings. Problem and Action Taken: Initial Inspection of the room did not, at once, Indicate what steps were reeded. It vus evident that the following conditions needed to be remedied: -- serious cracks and gaps where panels of the steel office partition Joined (it was possible to slip a business card "through the wall" in several of these places) -- serious gaps around a "soundproof" door -- flanking paths through ventilating duct* cocoon to other rocos - low transmission loss through the steel panels themselves -- leakage through the masonry wall on the short end of the roc -- low transmission loss through the one-way mirror to the observation room Subsequent remedial steps and testing revealed that all these were, in truth, serious sources of sound leakage. Gut, in addition, the WITT LIA 24038 Bergen County Polygraph Rocn -4- Kcrch 9* 1964 following conditions were suspected early in the project: -- leakage through ceilings into the plenum between the hung plaster celling and the slab above and then through the celling of the polygraph room -- leakage through the hollow floor slab in wiring raceways -- leakage around fluorescent fixtures and celling grills from the plenum While all of these sound paths no doubt contribute to the lack of acoustical Isolation, their contribution, in the light of the final results, Is Judged to be minor. Because of the great number of apparent conditions to be handled, there were some false starts on planning a soundproofing procedure. The plan finally agreed andcalled for these steps to be taken: -- four-pound sheet lead to be adhered directly to the three steel walls of the room with a viscoelastic ("Contact" type) cement -- furring strips to be fastened oyer the masonry wall with four-pound lead over them, all seams to be sealed with cement In lap Joints in addition to nailing to the furring -- filling the space between the furred out lead and the masonry wall with glass fiber or mineral wool -- gasketing the door -- blocking the air return of the adjacent office with four-pound sheet lead to close the leakage path through the ccroon duct (ventilation for the adjacent office by undercutting its door) -- lining the feed and return air ducts of the polygraph room with about 10 square feet each of glass fiber Conventional construction procedures were used throughout. The sheet lead for the steel walls was cut into square "tiles" 20 inches on a side. (This happened to be a convenient module for the mcra dimensions and the tiles were Judged to be easily handled.) The lead was washed with an alkaline cleaner and flushed with water. This removed any oil and produced a matte surface which accepted adhesive well. Tiles were cemented in place by painting cement on the tile and the wall in the area to be covered. Starting at the mqpboard, each tile was positioned so that its bottom edge wae In place, and then eased up against the wall. In higher rows, previously set tiles were used to align the new ones. At comers, the lead was dressed to give a tight fit into the comer where it Joined the dissimilar masonry wall or butted at the steel wall comers and later calked. -more' . LIA2A039 Bergen County Polygraph Rood .-.rci: 9, 1964 It had been hoped that the seams of the tile* could t calked, smoothed and painted vlth texture paint for a satisfactory surface finish on the steel valla. This proved to be too difficult to do. Furthermore, tapping of the lead tiles with short lengths of plank to moke aure the adhesive bond was bubble-free had scarred the surface of the lead to an extent where paint could not cover the blemish. Various finishing materials were considered and acoustical ceiling tile was used because it waa available and because it was thought that with it the room would have a deadness, or lack of reverberation, which night prove helpful. (In the opinion of Bolt, Beranek and Hevnan, who later onalyted the resulta of test on the room, if acoustical tile had not been used, the roots night have been satisfactory for its purpose without the introduction of masking noise thi ugh this cannot be stated definitely on the baala of the test* which vet t made.) It had been planned to surface the short masonry wall with hooosebe wallboard over the lead and acoustical tile finish in any event, and thi# procedure was followed. It Is worth noting that the two carpenters who worked on this Job were county eeployees and had not had any previous expericnc" with sheet lead. Their work was quite good fr'co the start and they had no difficulty in dressing lead into and around corners -- Including the forming of a "frane" for the one-way mirror which shows in the finished Job. Resulta; Several sets of tests were made. The first tests were made before any work vas started and represent the condition of the rooa with no treatment other than calking the cracks. Host of the intense liate tests were concerned with checking out various schemes for gasketing the door. The final set of tests were made after the door gaskets and the room had teen in service for about six months and so represent the real improvement after the sound proofing had been subjected to some normal wear and tear. The following test results were obtained; -more- LIA24040 Bergen County Polygraph Rocc -6- March 9, 1964 NOISE REDUCTION ACHIEVED (Eased on teats with a 25 watt Crayson-Stodtler noise generator and an Industrial Acoustics Corp. Sound Spectrometer, octave band Instrument -- NR at the stated frequencies estimated frai the plotted data) Freq. cps From HALL to POLE NR In decibels Frco ADJACENT OFFICE to POLE NR In decibels Frco OBS. RH. to POLY NR in decibels before after diff. before after diff. before after diff. 125 170 250 350 500 700 1000 2000 4000 18.5 19.5 21.5 24 26 27.5 28 25 23 30 33 36.5 40.5 42.5 43.5 45 47 47 11.5 13.5 15 16.5 16.5 16 17 22 24 18 23 28 33 36 37.5 39 40 39.5 34 37.5 40 42 44.5 46 48 52.5 52.5 16 14.5 12 9 7.5 8.5 9 12.5 14 28 29-5 32 35 36.5 37.5 39.5 42 36 30.5* 31 * 35 4l 44 55 48 50 50 2.5 1.5 3 6 7.5 8.5 8.5 8 14 average (9 freq.) 23-5 40.5 17 32.5 44 11.5 35 41.5 6.5 *Vhen plotted, the "after" curve for Noise Reduction frao the Observation Roco to the Polygraph Room shows a noticeable dip In this region. The dip Is thought to represent the leak through the one-way glass mirror. No remedial action was taken in this case for two reasons: first, the average noise reduction from the observation roca to the polygraph room is good and this dip does not occur In a critical portion of the sound spectrum, and, second. It can be safely assumed that during a test tie occupants of the observation room. If any, will take care to be reasonably quiet. As has been pointed out, the noise reduction achieved is generally good, but the polygraph root had become so quiet that even the small amount of sound leaking In was quite noticeable. For this reason a 15 Inch fan la used In the polygraph roca to provide a high enough ambient noise level to mask these Incoming sounds. The real test of whether this works la listening. In order to demonstrate it on paper, however, the following test was run. The noise source was adjusted In the observation roca to the spectrum shown. This noise intensity roughly approximates the nolas of a subway train. The fan was run In the polygraph roca and the octave band sound levels were recorded there under these conditions. These were compared to the ambient noise with -'.he fan running but without the noise source running in the observation roaa. 0 -more* TV rrr 1F~ 'm.i-- MJ' i h j iu u p^iu j w LIA2A0A1 Bergen County Polygraph Roca -7- March .'964 The following results were obtained! OCTAVE BAUD BOISE LEVELS Ut DECIBELS Freq. band (cps) 37.5 75 75 - 150 150 - 300 300 - 6oo 600 - 1200 1200 - 2400 2400 - 4800 4800 - 9600 Source in Cfct. Room 73-5 71 74 8749 88 66 80 Total in Poly. Room 6527 4562 45 43 36 27 Fan Chly In Poly. Roca 52 63 52 46 46 41.5 35 27 Difference (in Poly. Roca) 5 -1 0 0 -1 1.5 1 0 it is generally accepted that In tests of this type differences of less than 6 db are not significant. With the exception of the difference (5 db) in the first band, all differences car. be assigned to experimental error. The first band difference nay, and probably does, represent sound leaking Into the polygraph room. It Is Judged to be a very minor leak and not troublesome In the Intended use of the rooa. Conclusions; The results achieved In soundproofing the polygraph rocn have been excellent. Detective Allners is well pleased with the rocn and has no rere---ations about its acoustical performance. The materials and direct l.to.~ costs, it Is felt, were not excessive in terms of what was accomplished. 2n the other hand, the amount of care, supervision, and detail work by those directing the project was considerable. Much of the technical and jnervUory labor can be accounted for by testing, cf course. But, in fairness, it must be said that the existing results would not have been achieved without a good many man-hours of experimenting and testing of provisional measures. Thla detailed technical work showed that the general scheme employed was co-aid csd vi rV.ble. The t tal m'.-.erl-ils and direct labor costs exclusive cf supervisory, testing, cr.d experiment, were about $1000. The findings of the LIA staff in this case have been reviewed and found substantially correct. Respectfully submitted, 0 BP:bd "mice Rader ' Manager, Technical Services i i mtpi**' LIA24042 ____________ _________________ _____ ___________ _____ ____________________________________________________ __________________ _______________________ -- Oo i \...................... 0 Pag* 3 nnjvjinpif BP UV ,J-!JJ"MWJ|M iiJUipiJLi * T* m*lMLfl !.'* * I I PUJ' I1 Y 11 // l 1 >TJfJWpWH^Pipi *mmH( LIAZ4043 QQ o P*ge 9 J?6ST5i 3wO<aD W (Trt ,-4-LO. 5v*Ct USAfc if /I -Doers UNet> u)(TH \o -M.FT. MirJlBAU NAOOU uANfCeY ..-4-l-a -SHEET iiAo\^ ON >'/tXVr* FOl*J^ \ >M0EAt VJOOx. CSertlMtJ 5* HOMoSOTC ove2. AGOOVTiCA*- Tn.E FINISH ti)E^<3eM CoUMTY Po l y g r a p h R.o o a a AFTR TeEATMNT \o^/c.s n<rr t o s c al e u a ^nLes" o f 4-LB. CAO dgMEWTEQ TO XIST|M<S WALL AtfooiTtfAL TU6 FINISH Doofi GAS*E.TTCt> M o n e K eD ucTtoisl L IA 24045 i i * wp I flM" *=** LIA2A0A6 O O f. N lcM ^S . 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