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7. NOISE |
7.1 INTERIOR NOISE AND VIBRATION TESTS
7.1-I. TEST OBJECTIVE
The
objective of these tests is to measure and record interior noise levels and
check for audible vibration under various operating conditions.
7.1-II. TEST DESCRIPTION
During
this series of tests, the interior noise level will be measured at several
locations with the bus operating under the following three conditions:
1. With
the bus stationary, a white noise generating system shall provide a uniform sound pressure level equal to 80 dB(A) on the
left, exterior side of the bus. The engine and all accessories will be switched off and all openings
including doors and windows will be closed. This test will be performed at the ABTC.
2. The
bus accelerating at full throttle from a standing start to 35 mph on a level
pavement. All openings will be
closed and all accessories will be operating during
the test. This test will be
performed on the track at the Test Track Facility.
3. The
bus will be operated at various speeds from 0 to 55 mph with and without the
air conditioning and accessories on. Any audible vibration or rattles will be noted. This test will be performed on the test
segment between the Test Track and the Bus Testing Center.
All
tests will be performed in an area free from extraneous sound-making sources or
reflecting surfaces. The ambient
sound level as well as the surrounding weather conditions will be recorded in
the test data.
7.1-III. DISCUSSION
This
test is performed in three parts. The first part exposes the exterior of the vehicle to 80.0 dB(A) on the
left side of the bus and the noise transmitted to the interior is measured. The overall average of the six
measurements was 54.7 dB(A); ranging from 54.1 dB(A) at the front passenger
seats to 55.9 dB(A) at the rear passenger seats. The interior ambient noise level for this test was < 34.0
dB(A).
The
second test measures interior noise during acceleration from 0 to 35 mph. This noise level ranged from 73.6 dB(A)
at the front passenger seats to 74.6 dB(A) at the middle passenger seats. The overall average was 74.3
dB(A). The interior ambient noise
level for this test was < 34.0 dB(A).
The
third part of the test is to listen for resonant vibrations, rattles, and other
noise sources while operating over the road. No vibrations or rattles were noted.
INTERIOR
NOISE TEST DATA FORM
Test
Condition 1: 80 dB(A) Stationary
White Noise
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Bus
Number: 0706
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Date:
5-10-07
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Personnel:
S.C. & T.S.
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Temperature
(°F): 76
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Humidity
(%): 65
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Wind
Speed (mph): Calm
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Wind
Direction: Calm
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Barometric
Pressure (in.Hg): 30.11
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Initial
Sound Level Meter Calibration: ■ checked by: S.C.
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Interior
Ambient
Noise
Level dB(A): < 34.0
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Exterior
Ambient
Noise
Level dB(A): 44.6
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Microphone
Height During Testing (in): 48.0
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Measurement
Location
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Measured
Sound Level dB(A)
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Driver's
Seat
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54.5
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Front
Passenger Seats
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54.1
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In
Line with Front Speaker
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55.0
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In
Line with Middle Speaker
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54.4
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In Line
with Rear Speaker
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54.3
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Rear
Passenger Seats
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55.9
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Final
Sound Level Meter Calibration: ■ checked by: S.C.
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Comments: All
readings taken in the center aisle.
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INTERIOR
NOISE TEST DATA FORM
Test
Condition 2: 0 to 35 mph
Acceleration Test
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Bus
Number: 0706
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Date:
8-29-07
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Personnel:
B.S., T.S. & S.C.
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Temperature
(°F): 70
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Humidity
(%): 85
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Wind
Speed (mph): Calm
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Wind
Direction: Calm
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Barometric
Pressure (in.Hg): 30.15
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Initial
Sound Level Meter Calibration: ■ checked by: S.C.
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Interior
Ambient
Noise
Level dB(A): < 34.0
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Exterior
Ambient
Noise
Level dB(A): 41.1
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Microphone
Height During Testing (in): 48.0
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Measurement
Location
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Measured
Sound Level dB(A)
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Driver's
Seat
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74.4
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Front
Passenger Seats
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73.6
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Middle
Passenger Seats
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74.6
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Rear
Passenger Seats
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74.5
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Final
Sound Level Meter Calibration: ■ checked by: S.C.
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Comments: All
readings taken in the center aisle.
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INTERIOR
NOISE TEST DATA FORM
Test
Condition 3: Audible Vibration
Test
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Bus
Number: 0706
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Date:
8-29-07
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Personnel:
B.S., T.S. & S.C.
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Temperature
(°F): 70
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Humidity
(%): 85
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Wind
Speed (mph): Clam
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Wind
Direction: Calm
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Barometric
Pressure (in.Hg): 30.15
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Describe
the following possible sources of noise and give the relative location on the
bus.
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Source
of Noise
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Location
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Engine
and Accessories
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None
noted.
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Windows
and Doors
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None
noted.
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Seats
and Wheel Chair lifts
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None
noted.
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Comment
on any other vibration or noise source which may have occurred that is not
described above:
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None
noted.
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7.1 INTERIOR NOISE TEST
TEST
BUS SET-UP FOR 80 dB(A)
INTERIOR
NOISE TEST
7.2 EXTERIOR NOISE TESTS
7.2-I. TEST OBJECTIVE
The
objective of this test is to record exterior noise levels when a bus is
operated under various conditions.
7.2-II. TEST DESCRIPTION
In the
exterior noise tests, the bus will be operated at a SLW in three different
conditions using a smooth, straight and level roadway:
1. Accelerating at full
throttle from a constant speed at or below 35 mph and just prior to
transmission up shift.
2. Accelerating at full
throttle from standstill.
3. Stationary, with the
engine at low idle, high idle, and wide open throttle.
In
addition, the buses will be tested with and without the air conditioning and
all accessories operating. The
exterior noise levels will be recorded.
The test
site is at the PSBRTF and the test procedures will be in accordance with SAE
Standards SAE J366b, Exterior Sound Level for Heavy Trucks and Buses. The test
site is an open space free of large reflecting surfaces. A noise meter placed at a specified
location outside the bus will measure the noise level.
During
the test, special attention should be paid to:
1. The test site
characteristics regarding parked vehicles, signboards,
buildings,
or other sound-reflecting surfaces
2. Proper usage of all
test equipment including set-up and calibration
3. The ambient sound level
7.2-III. DISCUSSION
The
Exterior Noise Test determines the noise level generated by the vehicle under
different driving conditions and at stationary low and high idle, with and
without air conditioning and accessories operating. The test site is a large, level, bituminous paved area with
no reflecting surfaces nearby.
With an
exterior ambient noise level of 40.9 dB(A), the average test result obtained
while accelerating from a constant speed was 70.9 dB(A) on the right side and
76.3 dB(A) on the left side.
When
accelerating from a standstill with an exterior ambient noise level of 40.2
dB(A), the average of the results obtained were 68.8 dB(A) on the right side
and 71.0 dB(A) on the left side.
With the
vehicle stationary and the engine, accessories, and air conditioning on, the
measurements averaged 57.0 dB(A) at low idle, 61.7 dB(A) at high idle, and 71.7
dB(A) at wide open throttle. With
the accessories and air conditioning off, the readings averaged 0.3 dB(A) lower
at low idle and 0.4 dB(A) lower at wide open throttle. The exterior ambient noise level
measured during this test was 40.6 dB(A). Note; The air conditioning must be on to activated the high idle mode.
EXTERIOR
NOISE TEST DATA FORM
Accelerating
from Constant Speed
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Bus
Number: 0706
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Date:
8-29-07
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Personnel:
B.S., T.S. & S.C.
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Temperature
(°F): 72
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Humidity
(%): 85
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Wind
Speed (mph): Calm
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Wind
Direction: Calm
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Barometric
Pressure (in.Hg): 30.15
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Verify
that microphone height is 4 feet, wind speed is less than 12 mph and ambient
temperature is between 30°F and 90°F: ■ checked by: S.C.
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Initial
Sound Level Meter Calibration: ■ checked by: S.C.
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Exterior
Ambient Noise Level dB(A): 40.9
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Accelerating
from Constant Speed
Curb
(Right) Side
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Accelerating
from Constant Speed
Street
(Left) Side
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Run #
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Measured
Noise Level dB(A)
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Run #
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Measured
Noise Level dB(A)
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1
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71.0
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1
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75.4
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2
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70.9
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2
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75.8
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3
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70.8
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3
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76.8
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4
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70.8
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4
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75.2
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5
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70.7
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5
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75.7
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Average
of two highest actual
noise
levels = 70.9 dB(A)
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Average
of two highest actual
noise
levels = 76.3 dB(A)
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Final
Sound Level Meter Calibration Check: ■ checked by: S.C.
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EXTERIOR
NOISE TEST DATA FORM
Accelerating
from Standstill
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Bus
Number: 0706
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Date:
8-29-07
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Personnel:
B.S., T.S. & S.C.
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Temperature
(°F): 72
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Humidity
(%): 85
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Wind
Speed (mph): Calm
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Wind
Direction: Calm
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Barometric
Pressure (in.Hg): 30.15
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Verify
that microphone height is 4 feet, wind speed is less than 12 mph and ambient
temperature is between 30°F and 90°F: ■ checked by: S.C.
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Initial
Sound Level Meter Calibration: ■ checked by: S.C.
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Exterior
Ambient Noise Level dB(A): 40.2
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Accelerating
from Standstill
Curb
(Right) Side
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Accelerating
from Standstill
Street
(Left) Side
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Run #
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Measured
Noise Level dB(A)
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Run #
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Measured
Noise
Level
dB(A)
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1
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67.8
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1
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70.7
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2
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68.8
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2
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71.2
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3
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67.5
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3
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70.1
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4
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68.8
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4
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69.5
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5
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67.5
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5
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69.9
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Average
of two highest actual noise levels = 68.8 dB(A)
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Average
of two highest actual noise levels = 71.0 dB(A)
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Final
Sound Level Meter Calibration Check: ■ checked by: S.C.
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EXTERIOR
NOISE TEST DATA FORM
Stationary
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Bus
Number: 0706
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Date:
8-29-07
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Personnel:
B.S., T.S. & S.C.
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Temperature
(°F): 72
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Humidity
(%): 85
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Wind
Speed (mph): Calm
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Wind
Direction: Calm
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Barometric
Pressure (in.Hg): 30.15
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Verify
that microphone height is 4 feet, wind speed is less than 12 mph and ambient
temperature is between 30°F and 90°F: ■ checked by: S.C.
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Initial
Sound Level Meter Calibration: ■ checked by: S.C.
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Exterior
Ambient Noise Level dB(A): 40.6
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Accessories
and Air Conditioning ON
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Throttle Position
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Engine RPM
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Curb
(Right) Side
dB(A)
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Street
(Left) Side
db(A)
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Measured
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Measured
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Low
Idle
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705
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57.5
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56.5
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High
Idle
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1,159
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60.3
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63.0
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Wide
Open Throttle
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3,995
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70.7
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72.6
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Accessories
and Air Conditioning OFF
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Throttle Position
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Engine RPM
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Curb
(Right) Side
dB(A)
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Street
(Left) Side
db(A)
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Measured
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Measured
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Low
Idle
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703
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56.9
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56.4
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High
Idle
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N/A
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N/A
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N/A
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Wide
Open Throttle
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3,995
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71.1
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73.0
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Final
Sound Level Meter Calibration Check: ■ checked by: S.C.
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Comments:
A/C must be activated for high idle to run.
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7.2 EXTERIOR NOISE
TESTS TEST
BUS UNDERGOING EXTERIOR
NOISE TESTING
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