GMW-8467-2006.pdf

WORLDWIDE ENGINEERING STANDARDS Test Procedure Noise and Vibration GMW8467 Vehicle Interior Noise Tests Hydraulic Power Steering Noise © Copyright 2006 General Motors Corporation All Rights Reserved March 2006 Originating Department: North American Engineering Standards Page 1 of 9 1 Scope Note: Nothing in the specification supersedes applicable laws and regulations unless specific exemption has been obtained. Note: In the event of conflict between the English and domestic language, the English language shall take precedence. 1.1 Purpose. Determination of hydraulic power steering system noise. 1.2 Foreword. This procedure describes the noise measurement of the hydraulic-assisted power steering system. 1.3 Applicability. The test is applicable to passenger vehicles with hydraulic-assisted power steering system. Specific noise covered in this procedure includes: Hydraulic Power Steering Pump Noise Hydraulic Power Steering Gear Noise 1.3.1 This test procedure includes quantification of typical hydraulic power steering gear noises, such as hiss, squawk, and whistle. The frequency range for hiss is 1 to 4 kHz for structure borne noise and 4 to 12.5 kHz for airborne noise. Squawk, a type of closed loop instability, has a frequency range of 100 to 350 Hz. The frequency range for whistle is 4 to 9 kHz. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. None 2.2 GM Standards/Specifications. None 2.3 Additional References. Not applicable. 3 Resources 3.1 Facilities. Hemi-anechoic chamber. 3.2 Equipment. Sound level measuring device with free-field measurement microphone (spherical characteristic). Recording units and evaluation devices (order tracking analyzer, FFT analyzer) and a tachometer. Coarse patio plates with smooth pebbles, see Appendix A. Temperature meter. 3.3 Test Vehicle/Test Piece. The tests shall be performed on a vehicle that represents the current release status. The entire hose routing shall be checked prior to the test, to ensure that no accidental contact between hoses and surrounding components has occurred, and that any intentional contact (i.e. indexing features) is correctly represented. In the event of uncertainty as to whether contact is intentional or not, the responsible engineer must be contacted before the test proceeds. Any deviations (e.g. obvious faults) must be noted and corrected prior to testing. 3.3.1 The power steering system must be bled before measurements are taken. To achieve a proper bleed of the system, warm the fluid up to at least 75 C and use a Mityvac or equivalent to apply a vacuum of 20 inHg (max) to the reservoir for five minutes. Release the vacuum and check the fluid level against the dipstick or reservoir markings; add fluid if necessary. Warm the fluid up to at least 75 C again and commence testing. 3.3.2 For pressurized reservoirs only. Allow the fluid to cool down to ambient temperature before commencing the second warm-up procedure and testing. Do not remove the cap once the second warm-up has begun, or during testing. If the cap is removed during these phases the cool down must be repeated. 3.4 Test Time. Calendar time: 1 day Test hours: 8 hours Coordination hours 4 hours 3.5 Test Required Information. Record engine rpm (or PS-pump rpm) and overall noise. 3.6 Personnel/Skills. Engineer or qualified tech- nician with basic knowledge of acoustics. 4 Procedure 4.1 Preparation. Check the vehicle according to 3.3. Adjust tires pressures to nominal values (cold). GMW8467 GM WORLDWIDE ENGINEERING STANDARDS © Copyright 2006 General Motors Corporation All Rights Reserved Page 2 of 9 March 2006 Install measuring instruments. Place the front wheels of the car on the coarse patio plates. Microphones in complete car with standard microphone positions that are specified in Appendix B. Standard positions are LFRE and RF for left hand drive vehicles and RFLE and LF for right hand drive vehicles according to 1.4. Seats and headrests shall be adjusted to according to Appendix C. The vehicle is unloaded except for the driver and the test equipment. All windows, sliding roof and sunscreen are closed. The engine or PS-pump rpm should be measured by a tachometer. Connect the tachometer and microphones to the analyzer. Switch off the air conditioning. Heater blower turned off. Radio and other accessories turned off. 4.2 Conditions. 4.2.1 Environmental Conditions. Hemi-anechoic chamber. The temperature of the hydraulic fluid should be approximately 90°C when measuring the pump noise. The hissing noise should be measured at three different temperatures, 80°C, 100°C and 120°C. To reach these temperatures the car should be warmed up and the steering wheel should be turned repeatedly. It is important to check the temperature during the whole test. 4.2.2 Test Conditions. Deviations from the requirements of the procedure shall have been agreed upon. Such requirements shall be specified on component drawings, test certificates, reports, etc. 4.2.3 Vehicle Conditions. Check that the engine speed is stable and that the engine cooling fan is not cycling on/off during the actual data acquisition process. Verify that the windows, sunroofs, hood and trunk/tailgate are closed. 4.3 Instructions. Before the start of the test, the instrument settings and the vehicle settings shall be checked again. For data processing measuring instruments, the adjustments according to sections 5 shall also be performed from the start of the test. 4.3.1 Calibration Verification. Verify the calibration of the measuring instruments according to the operating instructions. Note the expiration date on the calibration label. Record calibration tone if applicable. The sound pressure level should be measured in dB(A) relative 20 Pa. 4.3.2 Measurement pre-test. Make a pre-test if necessary. 4.3.3 Measurement of pump noise with unloaded system. Operate the vehicle by running the engine from idle up to at least rated engine rpm or maximum useable rpm, with gear in “N“, during 60 seconds in a controlled manner. Record a sufficient number of sweeps (at least two) with the system unloaded, i.e. no steering angle, to get measurement spread. 4.3.4 Measurement of pump noise with loaded system. Operate the vehicle by running the engine from idle up to at least 5 000 rpm, with gear in “N“, during 60 seconds in a controlled manner. Record a sufficient number of sweeps (at least two) with the system loaded to the right, i.e. 1/6 of full steering angle (for Holden: See Deviation Appendix D), to get measurement spread. It is important to maintain steady pressure on the steering wheel through the sweep. 4.3.5 Measurement of gear noise at idle. Operate the vehicle in neutral at idle. With the steering wheel centered, record the interior noise for at least 16 seconds. Observe the worst position of the steering wheel for power steering hissing noise, usually about 1 + ¼ turn. This is conducted for two cases, the steering wheel turned to the left and turned to the right. At least two measurements of the interior noise are then obtained for at least 16 seconds at three different temperatures, specified in 4.2.1, for each of the cases. 4.3.6 Measurement of gear noise at 2000 ERPM. Operate the vehicle in neutral at 2 000 ERPM. With the steering wheel centered, record the interior noise for at least 16 seconds. Observe the worst position of the steering wheel for power steering hissing noise, usually about 1 + ¼ turn. This is conducted for two cases, the steering wheel turned to the left and turned to the right. At least two measurements of the interior noise are then obtained for at least 16 seconds at three different temperatures, specified in 4.2.1, for each of the cases. 5 Data 5.1 Calculations. The calculations shall be performed for the measuring instruments selected according to section 3.2. The associated vehicle and test condition documentation shall be included when entering the data. Analyze the noise as follows: All sound level calculations use the frequency weighting “A“. 5.1.1 Pump Noise. (For Holden: See deviation in Appendix D) Order tracking analysis with hanning weighting for the pump noise and FFT analysis with hanning weighting for the hissing noise. Select 0.1 ± 0.025 order as the order resolution to clearly identify the peaks from the fundamental tone and harmonics of the PS-pump (two through eight GM WORLDWIDE ENGINEERING STANDARDS GMW8467 © Copyright 2006 General Motors Corporation All Rights Reserved March 2006 Page 3 of 9 times the fundamental pumping order) over the whole sweep. A bandwidth order span of 0.5 ± 0.25 should be selected to receive the harmonics from the PS- pump (two through eight times the fundamental pumping order) over the whole sweep. 5.1.2 Gear Noise. FFT analysis with hanning weighting for the hissing noise. Select appropriate frequency resolution to clearly identify tonal peaks generated by the hissing noise. Appropriate bandwidth for the FFT analyser is 1 to 12.5 kHz. This bandwidth is then divided into two areas. The lower range, 1.3 to 4 kHz, is mostly structure born hissing through the steering shaft. The higher range, 4 to 12.5 kHz, is mostly a quite low noise level of flow from the steering rack valve. This sound is also more “Sound Quality”. The total sound pressure level for these two frequencies areas are then calculated as indices. 5.2 Interpretation of Results. Determine if VTS requirements are satisfied. 5.3 Test Documentation. Standardized formats, which are included in the Program Specific VTS and Global VTS Template, shall be used. 6 Safety This procedure may involve hazardous materials, operations, and equipment. This method does not propose to address all the safety problems associated with its use. It is the responsibility of the user of the method to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 7 Notes 7.1 Glossary. Not applicable. 7.2 Acronyms, Abbreviations, and Symbols. ERPM Engine Revolutions per Minute LF left front (seat vacant, microphone placed in center of seat position) LFRE left front seat, right ear (left hand drive vehicle, drivers seat occupied) RF r right front (seat vacant, microphone placed in center of seat position) RFLE right front seat, left ear (right hand drive vehicle, drivers seat occupied) 8 Coding System This material specification shall be referenced in other documents, drawings, VTS, CTS, etc. as follows: Test to GMW8467 9 Release and Revisions 9.1 Release. This test procedure originated in November 2001. The specification was approved in June 2003 by the Advanced Integration Interior Noise & Wind Noise Noise & Vibration Integration Center. It was first published in October 2003. 9.2 Revisions. Rev Approval Date Description (Organization) A OCT 2004 Added bleeding requirements, definitions of hiss, whistle, and squawk, extended frequency range to 12.5 kHz, changed name of hissing test to gear test. (Noise and Vibration) B MAR 2006 Formatting changes (Noise and Vibration) GMW8467 GM WORLDWIDE ENGINEERING STANDARDS © Copyright 2006 General Motors Corporation All Rights Reserved Page 4 of 9 March 2006 Appendix A Figure A1: Coarse patio plates with smooth pebbles GM WORLDWIDE ENGINEERING STANDARDS GMW8467 © Copyright 2006 General Motors Corporation All Rights Reserved March 2006 Page 5 of 9 Appendix B (0.7 ± 0.05) m (0.2 ± 0.02) m Measuring point LFRE Standard position for occupied seat Standard position for unoccupied seat Measuring points See Vehicle Preparation in the test procedure for microphone position standards used for this test procedure. Also reference the Regional Deviations for deviant standards used in specific regions. Figure A2: Coordinates of Measuring Points LFRE (occupied s RF LR RR eat) Seat Microphone RFLE (occupied seat) LF Figure A3: Definition of Possible Measurement Positions GMW8467 GM WORLDWIDE ENGINEERING STANDARDS © Copyright 2006 General Motors Corporation All Rights Reserved Page 6 of 9 March 2006 Appendix C Seat Location 1 Place microphone stand in seat with pivot against seat back. 2 Check that microphone is horizontal. 3 Adjust seat back to as vertical as possible while maintaining at least 15 cm from microphone. 4 Place seat in the full backward and full downward position. 5 Measure horizontally from the furthest forward point on the rear seat that is directly behind the front seat to the front seat back. 6 Move the seat to full forward, and repeat step 5. 7 Add the two distances (steps 5 & 6), divide by 2, move the front seat until the seat is located at the calculated distance from the rear seat. 8 Measure vertically from the furthest forward position on the front seat to the floor. 9 Raise the seat to its full upward position, and repeat measurement from step 8. 10 Add the two distances (steps 8 & 9), divide by 2. Move the seat all the way down and then raise it until the seat is located at the calculated distance from the floor. Record this dimension. 11 Measure horizontally from the furthest forward point on the rear seat that is directly behind the front seat to the front seat back. Record this position. -,-,- GM WORLDWIDE ENGINEERING STANDARDS GMW8467 © Copyright 2006 General Motors Corporation All Rights Reserved March 2006 Page 7 of 9 Deviations This test procedure shall be followed in its entirety with the exception of those deviations listed in the Regional Appendices found on the following pages. GMNA Regional Deviations: 4.3 Instructions. 4.3.1 Calibration Verification. 4.3.2 Measurement pre-test. 4.3.3 Measurement of pump noise with unloaded system. 4.3.4 Measurement of pump noise with loaded system. 4.3.5 Measurement of hissing noise. 5 Data 5.1.1 Pump Noise. Calculate the masking level for the fundamental tone and the harmonics (two through eight times the fundamental pumping order) by cutting the specific orders of the unloaded sweep with the appropriate bandwidth. Determine the best fit line through each order. This analysis shall be completed only if the unloaded sweep has acceptable noise levels. 5.1.1.1 Plot the fundamental tone and harmonics of the PS-pump (two through eight times the fundamental pumping order) versus the engine RPM for both microphone locations. This shall be done for the system loaded to the left and loaded to the right. Compare to the best fit line of the masking level for a specific order. 5.1.2 Gear Noise. 5.2 Interpretation of Results. The rms values from 1.3 to 4 kHz and from 4 to 12.5 kHz are the noise indices. Record these metrics for each of the three different temperature conditions (80°C, 100°C, and 120°C), the three different steering wheel positions (straight, left, and right), and the two different microphone locations. Compare to the VTS requirements. GMW8467 GM WORLDWIDE ENGINEERING STANDARDS © Copyright 2006 General Motors Corporation All