Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
H1 APPENDIX H MEDIUM TRUCKS DISCUSSION TABLE OF CONTENTS DISCUSSION OF MEDIUM TRUCK CONTOURS AND PROFILES ..............................H2 Northern California Test Sites .........................................................................................H2 North Carolina Test Sites .............................................................................................. H11
A total o following trucks. Northern As shown Northern at these s North Ca which wa Figure H Californi Lakevill it is diff variation from the Figure H truck cas vehicle concentra centered DISCUS f 83 mediu Appendix California in Tables 3 California s ites. As wit rolina sites, s 94.2 dBA 1: Overall a e Site. Due t icult to det from vehic maximum p 1 that is low e at Lakevil (Run 43), a tions are co on the drive SION OF M m trucks w discusses t Sites and 7 of th ites in Dece h the heavy have been n . A-weighted o the limite ermine wha le-to-vehicle rofile level est to the g le, which is re shown mpletely at axle tires a EDIUM T ere measur he contour e main repo mber 2013. truck runs, ormalized t levels for d number of t would be is large. Th by 10 dBA r round reduc shown in Fi in Figure H the ground nd one abo H2 RUCK CON ed at the 2 and profile rt, a total of Figure H1 the medium o the averag all medium medium tru considered e heights a ange from 4 ed by 10 dB gure 28 of th 2. The co level. Ther ut mid-way TOURS A 0 test sites analysis c 20 medium shows the p truck runs e maximum -duty vehi ck runs at e a âtypical t which thes .7 to 10.1ft A slightly e main repo ntours indi e appear to between th ND PROF included in onducted fo trucks were rofiles for a in Figure H profile leve cles measu ach site sho â profile fo e medium t (1.4 to 3.1m lower than rt. The cont cate that t be two sou e front and ILES this study. r these me measured a ll medium tr 1, as well l of all test red in Nor wn in Figur r each site. ruck runs re ). The prof the lowest h our plots fo he noise so rce regions drive axles. The dium t the ucks as all sites, thern e H1, The duce ile in eavy r this urce : one This
H3 second source region aligns with the muffler shown in the photograph, which is just behind the cab and low to the pavement. The highest one-third octave band levels occur in the 630 Hz contours, which clearly indicate drive axle tire noise as the source in this band. However, in the 800 Hz band, which has maximum levels 3 dB lower than 630 Hz, the tire noise and muffler sources are equal. For this truck, the exhaust outlet is elevated; however, there is no trace of noise from it in the contours for any of the one-third octave bands. As a result, the significant sources are both close to the pavement, producing the vertical profile of Figure H1. The contours for the medium truck run at Lakeville with the highest profile levels above the ground (Run 24) are shown in Figure H3. For this truck, the overall contours are expanded from those of Run 43, both vertically and horizontally, with the higher levels extending beyond the front bumper of the truck. The highest one-third octave band level occurs in the 315 Hz band, with the source region centered on the drive axle tires. These drive axle contours are expanded, much like those of Figure 24 of the main report for 315 Hz, and as a result, the overall levels are also expanded in this region. For 500 Hz, two source regions of equal strength are indicated at the drive axle tires and at the front of the truck. The region at the front of the truck is quite expanded compared to the drive axle, and the source region is positioned slightly higher, indicating powertrain-related noise. Similar to the truck of Run 43, Run 24 has a muffler located behind the cab and low to the ground. However, in this case, the source region extends well beyond the muffler area and more toward the front of the truck. At 1,000 Hz, the source region is skewed even more to the front of truck, indicating that powertrain noise is being radiated beneath the truck and through the front grille. As a result, the relatively constant shape of the overall contours and their expanded height distribution is due to the combination of high levels of drive axle tire noise at 315 Hz and powertrain noise at a higher source height at the front of the truck. In addition to engine noise from the front of the cab and at the ground level from under the cab, many of the medium truck contour figures showed noise radiating from the wheel well. The contours for Run 36 demonstrate this behavior in Figure H4. For this example, the higher frequency bands have a heavy noise concentration at the ground level with another noise concentration directly above ground level. At 3,150 Hz, the second noise source located approximately 3ft (0.9m) above the ground has slightly higher noise levels than the ground-level source. Additionally, this noise source is elongated, indicating possible noise contribution from the muffler, as well. This stacked noise source concentration behavior at the higher frequency bands was more common for medium trucks than for heavy trucks. However, due to the limited number of medium trucks in the data set, more testing would be required to verify the statistical significance of the behavior.
 Figure H2: Overall, 630, and 800 Hz cont H4 ours of med ium truck pass-by Run 4 3 at Lakeville
Figure H3: Overall, 630, and 800 Hz cont H5 ours of medium truck pass-by Run 24 at Lakeville
 Figure H Lakeville 505 SB2 505 SB2 truck pro increasin trucks, th 4: Overall, Site. The pr . While thes file (Run 10 g to levels j is secondary 500, 1,000 ofiles show e four truck 9) reduced ust passed peak indic , and 3,150 n in blue in s showed si to levels be 80 dBA at ated an elev H6 Hz contou Figure H1 r milar variat low 76 dBA heights abo ated noise s rs of mediu epresent the ion to the L at approx ve 12ft (3.7 ource in the m truck pa medium tru akeville tru imately 10.5 m). As disc exhaust sta ss-by Run 3 cks measur cks, one me ft (3.2m) b ussed for h ck region. B 6 at ed at dium efore eavy ased
H7 on the contours for this vehicle, which are shown in Figure H5, no elevated exhaust stack was apparent; however, there is a rack attached to the bed of the truck with an all-terrain vehicle mounted on it and protruding above the back of the truck cab. Aside from the elevated cargo noise source, the primary noise source for the medium truck of Run 109 appears to be from the drive axle tires, which seem to be quite pronounced in the 500 Hz band. This band also has the highest maximum level of all of the bands. Noise from the tires on the front axle, and possibly engine noise, appears to be less of a source. This vehicle is also pulling a trailer, and noise from its tires is significant compared to the other sources for the overall A-weighted contours. The profile for Run 93 from the 505 SB2 site, which does not include a secondary elevated source, reduced by 10 dBA at a height of 7.5ft (2.3m) and had a maximum height of about 9.1ft (2.8m). The contours for this run are shown in Figure H6. As shown in the figure, the noise contours from the drive axle, which extended to beyond the front of the truck, are constant and low to the pavement. For the 1,250 Hz band, tire noise from drive axle is indicated; however, front axle tire noise cannot be distinguished from engine noise. Since the contours at the front of the truck extend beyond the front bumper, engine noise may be passing through the grille opening and/or through the wheel well and underbody areas. In each medium-duty truck run at 505 SB2, some trace of engine noise was present. Typical heavy trucks measured at 505 SB2 reduced by 10 dBA at heights ranging from 5.6 to 9.8ft (1.7 to 3m), which is lower than the range of heights for the majority of the medium trucks measured at this site. This may be due to the varying operating conditions, considering the average measured speed of the medium trucks was 3 mph faster than those measured for the heavy trucks.
 Figure H SB2 5: Overall, 500, 800, and 3,150 Hz H8 contours of medium truck pass-by Run 109 at 505
Figure 505 NB1 profiles f identical profiles f Lakeville least two tire and which ap out. The While th profile al noise, an H6: Overa Site. A to or all three . These runs rom 505 NB and 505 SB source regi another ben pear to be d se indicate e contours f most identi d drive axle ll, 800, and tal of three vehicles ar reduced by 1 fall with 2 sites. Co ons are indi eath the cab ue the drive some drivel or the other cal to the R tire noise do 1250 Hz con medium-du e shown in 10 dBA at in the range ntours for R cated for th . The maxi axle tires. A ine noise an two mediu un 66 had minates the H9 tours of me ty vehicles Figure H1 heights ran found for t un 66 at Si is medium t mum conto t higher fre d engine n m trucks ar contours ind overall A-w dium truck p were meas in green. T ging from 6 he nine me te 505 NB1 ruck run: on ur levels oc quencies, a oise, particu e not provi icating ver eighted con ass-by Run ured at Sit wo of the r .5 to 7.5ft dium trucks are shown e centered curred in th reas closer t larly in the ded, the run y little engi tours. 93 at 505 S e 505 NB1. uns are virt (2 to 2.3m) measured a in Figure H on the drive e 800 Hz b o the truck 1,250 Hz b with an ov ne or power B2 The ually . The t the 7. At axle and, stand and. erall train
 Figure H NB1 Compare that fall The diffe 7: Overall, d to the hea within the r rence in av 800, 1,250, vy trucks a ange measu erage measu and 2,000 H t this site, th red for the red speeds H10 z contours e medium heavy truck between he of medium truck runs r s, which wa avy and me truck pass-b educe by 10 s 5.2 to 8.9 dium is abo y Run 66 a dBA at he ft (1.6 to 2 ut 1 mph, w t 505 ights .7m). hich
H11 may be contributing to the medium truck profiles showing similar behavior to the heavy trucks. Of course, the limited number of medium trucks measured at 505 NB1 limits the statistical relevance of the data set, which means that more trucks would have to be tested to determine if this pattern continues. North Carolina Test Sites Uphill Sites. As summarized in Table 7 of the main report, a total of ten medium trucks were measured at three of the uphill sites in North Carolina. Each of these medium trucks is shown in Figure H8. The profiles for the medium trucks measured at NC6 (shown in red in Figure H8) reduced by 10 dBA at heights ranging from 5.2 to 7.5ft (1.6 to 2.3m) and did not have any traces of noise sources above 8ft (2.4m). In contrast to the medium trucks at NC6, the medium truck profiles measured at NC11 (shown in blue in Figure H8) indicated considerable run-to-run variation. One profile reduced by 10 dBA at 5ft (1.5m) and flattened out at about 5.5ft (1.7m), while another medium truck reduced by 10 dBA at 10.8ft (3.3m) before flattening out at 11.1ft (3.4m). Due to this variation, it is difficult to determine what would be âtypicalâ behavior for medium trucks at this site. The one medium truck measured at NC13 reduced by 10 dBA at a height of approximately 6.3ft (1.9m); this profile (shown in green Figure H8) falls within the range of profiles measured at the other uphill sites. After reviewing the contours for the medium trucks measured at each uphill site, only one profile had traces of an elevated noise source. Compared to the heavy truck profiles at these sites, the medium truck profiles at NC6 and NC13 fall within the lower part of the range of heavy truck profiles, and the varying medium truck profiles at NC11 represent a similar range in heavy truck profiles.
 Figure H in North Downhil in North truck at t at Site N Run 24 a sources a at height medium trucks, di noise dis Comparin shown in maximum heights r 2.3m) at noise sou indicated the avera level at N NC12 red at NC13 8: Overall A Carolina l Sites. At l Carolina. T he downhill C10 (shown t the Lakev t or below 8 s between 5 trucks at the scussed pre tributions fo g the mediu green in F profile lev anging from the uphill s rces. Sites N that all nois ge maximum C13; howe uced by 10 reduced by -weighted east one me he profiles sites resulte in purple in ille site (see ft (2.4m) re .1 and 7.9ft downhill s viously, at S r the medium m trucks m igure H9) to el at the uph 5.1 to 6.5f ites. Medium C12 (down e sources w profile lev ver, there w dBA at heig 10 dBA at levels for al dium truck for these ve d in noise l Figure H9) Figure H3) duced from (1.6 and 2 ites were sim ites NC2, N trucks wa easured alo the uphill ill site was t (1.6 to 2m trucks at hill) and N ere below 8 el was appr as only on hts ranging 6.3ft (1.9m H12 l medium-d was measur hicles are s evels at a he . The contou . All medium the maximu .4m). Simila ilar to the C4, NC7, a s the same r ng the down site (NC6 s 1 dBA grea ) at the dow both sites d C13 (uphill) ft (2.4m). A oximately 0 e medium tr from 5.6 to ), which fal uty vehicles ed at each o hown in Fi ight above rs for this t trucks at m profile le r to the uph lower range nd NC12. A ange observ hill site on hown in red ter, and the nhill sites id not indic , which both t NC12 (sho .2 dBA high uck measur 6.5ft (1.7 to ls within th measured a f the five d gure H9. O 8ft (2.4m), a ruck were s the downhil vel at the gr ill sites, th of profiles t NC10, the ed for typica I-74 in Nort in Figure profiles redu and from 5. ate the pres had DGAC wn in oran er than the m ed at NC13 2m), and t e range of t t the uphill ownhill test nly one me nd this occ imilar to tho l sites with ound by 10 e profiles fo for typical h range of ve l heavy truc h Carolina ( H8), the av ce by 10 dB 2 to 7.5ft (1 ence of elev pavement ge in Figure aximum pr . The profil he medium he downhill sites sites dium urred se of noise dBA r the eavy rtical ks. NC7 erage A at .6 to ated , also H9), ofile es at truck site.
The uphi had aver slightly h profiles r profiles a height ra resulted i pair. How measured Figure H sites in N Level Sit level gra figure do review o to be the mid-heig The rang trucks sh ll and down age maximu igher. Both educed by t NC10 redu nges at NC n greater va ever, concl at these sit 9: Overall orth Carolin es. Medium de, and the p not indica f the contou drive axle hts, there w e of medium own in Figu hill sites al m profile l of these sit 10 dBA at ced by 10 d 10 are sligh riation in ve usions cann es. A-weighted a trucks wer rofiles for t te any nois rs for these tires with so as some ind truck prof re 44 of the ong the grou evels within es resulted i heights rang BA at heigh tly lower th rtical distrib ot be drawn levels for a e only meas hese trucks e contributi medium tru me engine ication of s ile distribut main body o H13 nd PCC pa 0.5 dBA o n a wide ra ing from 5 ts ranging f an at NC11 utions of no based on th ll medium- ured at one are shown i ons at elev cks, each ru noise contri ome elevat ions at NC1 f the report vement (NC f each othe nge of profi to 10.8ft ( rom 4.9 to 8 , it is intere ise levels th e limited sa duty vehicle site in Nor n Figure H1 ated source n identified bution. For ed noise at 5 fall within . 11 and NC r, with the le results. A 1.5 to 3.3m .5ft (1.5 to sting that bo an any othe mple size o s measured th Carolina 0. The prof s above 9ft the domina the runs wi the higher f the typical 10, respecti uphill site b t Site NC11 ). Medium 2.6m). Whil th of these r downhill/u f medium tr at the dow with a relat iles shown i (2.7m). Af ting noise so th some no requency b range for h vely) eing , the truck e the sites phill ucks nhill ively n the ter a urce ise at ands. eavy
 Figure H in North Slower S indicate instance, Figure H had an a reduced f 3.4m), w at height heavy tru have som would be had eleva the mediu low frequ The med average m average measured truck pro 3m). In c from 5.1 noise lev 10: Overall Carolina peed Sites. a closer co the profiles 11, had an a verage max rom the gro hile the pro s ranging fr cks at Site N ething to d required to ted noise so m trucks te ency conten ium truck p aximum pr maximum p truck speed files reduce omparison, to 10.6ft (1 els within 1 A-weighted The vertica rrelation to of the med verage max imum prof und-level m files for the om 4.8 to 9 C8 was app o with the make such urces within sted indicat t at the 315 rofiles meas ofile level f rofile level was only 1 d from the m the typical .6 to 3.2m) 0 dBA of th levels for a l noise distr the profiles ium trucks imum profil ile level of aximum by medium tru .6ft (1.5 to roximately correlation; a conclusio 10 dBA of ed the prese Hz band. ured at Site or the medi for the he .3 mph, wit aximum by heavy truck . At NC14, e maximum H14 ll medium- ibutions for for heavy measured a e level of 91 91.8 dBA. 10 dBA at h cks shown i 2.9m). The 8.4 mph slo however, a n. While 19 the maxim nce of eleva NC14 are um trucks w avy trucks h the heavy 10 dBA at s at NC14 13% of the profile lev duty vehicle medium tru trucks than t Site NC8 dBA, whil Likewise, eights rang n red in Fig average me wer than th greater sam % of the he um profile l ted sources shown in bl as approxim at this site trucks being heights ran reduced by heavy truck el, but ther s measured cks at the s the faster , which are e the heavy typical heav ing from 5.1 ure H11 red asured vehi e medium tr ple size o avy trucks m evel at grou . However, t ue in Figure ately 1.9 d , the differ slightly fas ging from 4 10 dBA at s had eleva e were no m at the level lower speed speed sites shown in r trucks at thi y truck pro to 11.2ft (1 uced by 10 cle speed fo ucks, which f medium tr easured at nd level, no he one truck H11. Whil BA less tha ence in av ter. The me .5 to 9.8ft (1 heights ran ted sources edium truc sites sites . For ed in s site files .6 to dBA r the may ucks NC8 ne of had e the n the erage dium .4 to ging with ks at
H15 this site that indicated the presence of elevated sources. Similar to NC8, however, one truck did have low frequency content. NC14 and NC13 both consist of DGAC pavement on a slight upgrade but with varying average speeds. At NC13, the speed was 66 mph for the one medium truck measured, and at this site, the profile level reduced by 10 dBA at a height of 6.3ft (1.9m). The average speed for medium trucks measured at NC14 was approximately 29 mph slower than at Site NC13, and the profile levels reduced by 10 dBA at heights ranging from 4.5 to 9.8ft (1.4 to 3m). The final slower speed site in North Carolina had a medium truck count of nine, and the profiles for these trucks are shown in green in Figure H11. The average maximum profile level at this site was 89 dBA for the medium trucks, which was approximately 4.7 dBA lower than for the heavy trucks, and the average measured speed limit was 52.4 mph, which was approximately 1 mph slower than for the heavy trucks. For the medium trucks shown at NC16, the profiles reduced by 10 dBA at heights ranging from 4 to 7.6ft (1.2 to 2.3m). Typical heavy trucks at this site reduced by 10 dBA at heights ranging from 5.1 to 10.7ft (1.6 to 3.3m). None of the medium trucks measured at NC16 indicated the presence of elevated noise sources. NC15 had a similar type of pavement on a level grade and a posted speed limit 10 mph faster than Site NC16. The medium trucks at NC15 reduced from the maximum profile level by 10 dBA at heights ranging from 4.5 to 9.8ft (1.4 to 3m), which were higher than the range measured for medium trucks at NC16. The average speed at NC15 was also 12.1 mph faster than at NC16, which may have influenced the vertical noise distributions. NC16 and Lakeville were both two-lane highways with relatively level grades, and vehicles at both sites were operated under cruise conditions. Similarly, the medium trucks at both sites had average speeds within 1 mph of each other. At the Lakeville site, the medium trucks reduced by 10 dBA at heights ranging from 4.6 to 9.2ft (1.4 to 2.8m), which is higher than at NC16. The cause of this discrepancy is unclear and further testing would be required.
 Figure H speed site 11: Overal s in North C l A-weighte arolina d levels for H16 all medium -duty vehicles measured at the slower
