Small craft -Measurement of sound pressure level of airborne sound emitted by powered recreational craft

Transcription

1 Small craft -Measurement of sound pressure level of airborne sound emitted by powered recreational craft Introduction This Standard describes the method for determining the pass by sound level emitted by powered recreational craft operating according to ISO (E4 or E5). It also specifies a simplified method for monitoring whether the sound pressure level of the craft has changed since type testing or after modification, and a method for measuring the sound pressure level at the shoreline caused by craft. The same outboard motor when mounted on different craft may produce different sound levels. Therefore five "standard craft" are specified to improve the comparability of results when testing outboard motors. The purpose of this standard is to allow a quantitative classification of the sound level emitted by powered recreational craft under typical operating conditions. ICOMIA /1

2 Contents 1 Scope References Definitions Type tests Monitoring tests Environmental tests Measurement parameters Measurement equipment Equipment specifications Equipment calibration Test site specifications and environmental conditions Test site Meteorological conditions Background sound pressure level Specifications for type and monitoring tests Test course Craft operation Operating conditions for type tests Operating conditions for monitoring tests Operating conditions for environmental tests Microphone positions Type tests and monitoring tests Environmental tests Type test procedure and monitoring test procedure Measurements Measurement validity Measurement distance -part throttle measurements Environmental test procedure Measurements Data analysis for type tests Five mode measurement -E4 duty cycle Five-mode measurement E 5 Duty Cycle Duty cycle pass by sound pressure level (Ldc) calculation Distance correction Test Report The nature of the tests Data of the propulsion unit...11 ICOMIA /2

3 15.3 Data of the craft, including standard craft Data on the operating conditions during the measurements Environmental conditions Instrumentation Quantities measured and measurement results Place, date of test and person responsible for the test Standard craft specifications for outboard motor type testing according to ICOMIA /3

4 1 Scope This ICOMIA Standard specifies the conditions for obtaining reproducible and comparable measurements of the pass by sound pressure level emitted by powered recreational craft including inboards, stern drives, Personal Watercraft (PWC) and outboard motors. It specifies the measurement of the sound pressure level when the craft is operated at each of the five modes of the ISO (E4 or E5) duty cycles. The measured levels can be quoted individually or can be combined to give the duty cycle pass by sound pressure level loc, The standard also specifies a simplified method for monitoring whether the sound pressure level of the craft has changed since type testing or after modification, and a method for measuring the sound pressure level at the shoreline caused by craft. It is intended as a guide toward standard practice and is subject to change to keep pace with experience and technical advances. NOTE -The test procedures specified in this International Standard are engineering methods as defined in ISO 2204, "Acoustics -Guide to the measurement of airborne acoustical noise and evaluation of its effects on man". Measurements made in accordance with this ICOMIA Standard result with few exceptions in standard deviations of reproducibility of the sound pressure level equal to or less than 1,5 db. 2 References IEC 179: IEC 651: 1979 "Precision sound level meters" "Sound level meters" IEC 651/A1:1993 "Sound level meters - Amendment 1 " IEC 942: 1988 ISO "Sound calibrators" "Reciprocating internal combustion engines -Exhaust emission measurement -Test cycles for different engine applications." IMEC 17 F/01 "Recreational motorboat sound level test report" - June 1993 IMEC 17 F/ "Powered recreational craft sound level test report" - May NMMA "Powerboat Sound Level Engineering Report" - October Definitions 3.1 Type tests Measurements performed to certify the sound level of the craft, or of an outboard ICOMIA /4

5 motor when using a standard craft. 3.2 Monitoring tests Measurements performed to check the sound level of the craft or of an outboard motor has not changed since type test certification or after modification, as applicable. 3.3 Environmental tests Measurements performed in order to ensure that the craft is not being operated in a manner that causes the sound level at the shoreline to be excessive according to local requirements. 4 Measurement parameters All readings of the sound level meter are to be taken with the time weighting characteristic "S" (Slow). The values to be measured at all microphone positions are A-weighted sound pressure levels L pa expressed in decibels (db). 5 Measurement equipment 5.1 Equipment specifications The instrumentation system including microphones and cables and the overall electroacoustic performance of any additional measuring equipment including for example a tape recorder and/or level recorder shall meet the requirements for a Type 1 instrument specified in IEC 651. Note - Sound level meters with "maximum hold" capabilities should be preferred. When a tape recorder is used for the measurements the dynamic of the instrumentation shall be consistent with the measured signal. A microphone windscreen that does not affect the overall reading by more than ±0,5 db(a) shall be used for all measurements. A sound level calibrator which meets the requirements of IEC 942 shall be used. A wind speed anemometer which is accurate to within ±2 meters per second shall be used. An engine speed tachometer which is accurate to within ±50 revolutions per minute (rpm) shall be used. ICOMIA /5

6 5.2 Equipment calibration The overall acoustic performance of the measurement equipment shall be checked according to the instructions of the manufacturer with a sound level calibrator at the beginning and at the end of each series of measurement and not less than the beginning and end of each day. At time-intervals no longer than 2 years, the sound level meter shall undergo laboratory verification for compliance with IEC 651. The date of the last verification of the compliance with the relevant IEC standard shall be recorded. 6 Test site specifications and environmental conditions 6.1 Test site The test site shall be such that sufficient free sound propagation exists. This condition may be considered as fulfilled if the surroundings of the microphone up to 100 metres are free of large, sound reflecting objects like barriers, hills, rocks, bridges or buildings. In the vicinity of the microphone; there shall be no obstacles which could disturb the sound field. Therefore, no person shall be between the microphone and the sound source, and any observers shall be in such a position that influences on the reading of the meter are avoided. For type testing and compliance monitoring, the area between the craft under test and the measuring microphone shall be open water or land surface free from any other sound-absorbing or sound-reflecting objects. For environmental testing the measuring microphone shall be placed as far as possible away from any sound absorbing and sound reflecting objects. 6.2 Meteorological conditions Meteorological conditions having an adverse effect on the microphone used for the measurements shall be avoided. Tests should only be performed under the following conditions: -absence of precipitation -wind velocity less than 5 meters per second 6.3 Background sound pressure level The A-weighted background sound pressure level which. is the noise from all sources other than the craft (for example waves splashing on the measurement craft or the shore, other craft or equipment and wind effects) shall be at least 10 db below the Aweighted sound pressure level of the craft. ICOMIA /6

7 7. Specifications for type and monitoring tests 7.1 Test course Three markers (buoys or posts) shall be placed in a straight line, 50 metres apart, to mark the course the craft is to follow while being tested. 7.2 Craft operation All craft shall be operated with a two person load or its equivalent, except any craft intended for one person as well as PWC which shall have an equivalent one person load, and a minimum fuel load of 10 litres. An equivalent one person load is defined as 75 to 85 kilograms. The outboard motor operating conditions (fuel used, run-up time, etc.) shall comply with the manufacturer s instructions. Craft with the engines installed inboard (e.g., inboards, stern drives, PWC and sailboats) shall be tested as sold for both type and monitoring tests. Outboard motors shall be tested on standard craft as specified in clause 16 for type testing, and as installed for monitoring testing. For propulsion systems which are equipped with adjustable trim, the trim angle shall be adjusted so that the propeller/impeller thrust is parallel to the plane of the hull within ±2, hereafter referred to as "level" trim for all test conditions. The propeller shall be selected such that at full throttle the engine speed falls within ±4% of the declared engine speed at level trim. In the case of spark-ignition engines without speed governor the declared engine speed shall be the mid-point of the full throttle speed range recommended by the manufacturer for propeller selection. In the case of engines with speed governors the declared engine speed shall be the governed speed specified by the manufacturer. While operating the engine as specified in 7.2, 8 and 9, the side of the craft nearest the microphone shall pass on the far side of all three markers within a distance of 2 metres on a course parallel to the line of markers. Caution must be exercised to avoid hitting the course markers. 8 Operating conditions for type tests The engine speed (in rpm) shall be as stated in ISO (Test cycles E4 & E5) for the five modes as percentages of the declared engine speed. Although all five modes must be measured in order to obtain the duty cycle pass by level Ldc, individual modes can be measured alone if required. Measurements may also be performed at other engine or boat speeds as required. (Note -The E-4 Duty Cycle is for spark ignition engines and the E-5 Duty Cycle is for compression ignition engines.) ICOMIA /7

8 Table 1 - Engine speed Duty cycle E4 E5 Mode 1 idle idle Mode 2 40% 63% Mode 3 60% 80% Mode 4 80% 91 % Mode % 100 % 9 Operating conditions for monitoring tests The operating condition is Mode 3 (60 %) of the declared engine rpm per the E4 duty cycle. The operating condition is Mode 2 (63 %) of the declared engine rpm per the E5 duty cycle. 10 Operating conditions for environmental tests The operating condition does not require that the craft be operating in any specific manner. 11 Microphone positions 11.1 Type tests and monitoring tests + The microphone shall be placed metres from and facing the line determined by the three markers as specified in 7.1, normal to the line and opposite the center marker. It shall be positioned between 1,2 and 1,5 metres above the water surface, and not less than 0,6 metres above the surface of the shore, dock or platform. It is preferable that the microphone is positioned above the water surface but if positioned on a dock or platform the microphone shall be placed near or beyond the end of the dock or platform Environmental tests The microphone shall be located along the shoreline at a distance of not less than 1 0 metres from the craft and shall be positioned between 1,2 and 1,5 metres above the water surface. ICOMIA /8

9 If located on a dock or platform the microphone shall be positioned near or beyond the end of the dock or platform and not less than 0,6 metres above the surface on which it is located. 12 Type test procedure and monitoring test procedure 12.1 Measurements The meter shall be observed as the craft passes through the test course as specified i n 7.1, 7.2 and 8. The applicable reading shall be the maximum sound pressure level measured during the pass-by. The observer shall record the applicable reading and the background sound pressure level taken immediately before and immediately after the applicable reading. At least two measurements shall be made for each side of the craft. The sound pressure level for each side of the craft shall be the average of the first two readings for each side which are within 1 db of each other. The sound pressure level reported shall be that of the louder side of the craft Measurement validity A measurement is valid only if the background sound pressure level is at least 10 db{a) below the applicable reading. The background sound pressure level includes wind effects, noise from craft other than the one being measured, wave action, craft wakes and other extraneous noises Measurement distance -part throttle measurements For measurements taken at reduced engine speeds as specified in 8 and 9 it may be necessary to compensate for the low sound pressure levels by moving the microphone to a position which is closer to the craft without venturing into the near field. Consequently, for craft less than 6 metres in length, the microphone may be placed at a distance of 12,5 metres from the test course when the measured level at 25 metres is less than 10 db above the background level as specified in 6.3. The maximum Aweighted sound pressure level measured at 12,5 metres shall be normalised to a distance of 25 metres as given in Environmental test procedure 13.1 Measurements The applicable reading shall be the maximum sound pressure level measured during the time when the background sound pressure level is at least 10 db lower than the craft being measured. ICOMIA /9

10 The observer shall record the applicable reading and the background sound pressure levels taken immediately before and immediately after the applicable reading. 14 Data analysis for type tests 14.1 Five mode measurement -E4 duty cycle In Table 2, input "Li" the maximum A-weighted sound pressure levels normalised to 25 metres according to 14.4, for each of the modes i =1 to i =5, and calculate L dc from the equation in Table 2 -E4 Duty Cycle Mode % of Li Time i rated rpm db(a) Fraction - ti 1 Idle... 0,4 2 40%... 0, %... 0, %... 0, %... 0, Five-mode measurement E 5 Duty Cycle In Table 3, input "Li" the maximum A-weighted sound pressure levels normalised to 25 metres according to 14.4, for each of the modes i =1 to i =5, and calculate L dc from the equation in Table 3 E5 Duty Cycle Mode % of Li Time i rated rpm db(a) Fraction - ti 1 Idle... 0,3 2 63%... 0, %... 0, %... 0, %... 0, Duty cycle pass by sound pressure level (Ldc) calculation Calculate the duty cycle pass by sound level by substituting the appropriate values into the following: L = 10 log dc 5 Li = t 10 i i ICOMIA /10

11 14.4 Distance correction If the distance between the microphone and the centre marker is set at 12,5 metres the measured maximum A-weighted sound pressure level for each pass-by shall be normalised to 25 metres by subtracting 5 db to obtain L i. Note: The figure of 5 db has been found appropriate from the results of many tests under similar conditions. (IMEC 17 F/01, IMEC 17 F/02, NMMA Powerboat Sound Level Engineering Report) 15. Test Report The test report shall include a reference to this International Standard and all relevant details concerning: 15.1 The nature of the tests a) Type test, Monitoring test and Environmental test Data of the propulsion unit a) Manufacturer b) Motor type and serial number c) Rated propeller shaft power according to ISO 8665 d) Rated engine speed e) Spark ignition or Diesel 15.3 Data of the craft, including standard craft a) Manufacturer b) Craft type and HIN Number (according to ISO 10087) c) Length (metres), beam (metres) and hull material d) Total weight as tested (kilogrammes) 15.4 Data on the operating conditions during the measurements a) The engine speeds at which the measurements were performed ICOMIA /11

12 15.5 Environmental conditions a) Weather conditions including but not limited to the wind direction and speed. b) Water conditions 15.6 Instrumentation a) Testing equipment used, including details on name of product, type, serial number and manufacturer b) Calibration method used, date and place of calibration 15.7 Quantities measured and measurement results a) The background sound level. b) The distance of the microphone from the test course. c) The maximum A-weighted sound pressure levels normalised to 25 metres (Li ). d) The duty cycle pass by sound pressure level (Ldc). e) The monitoring test sound level according to Place, date of test and person responsible for the test 16 Standard craft specifications for outboard motor type testing according to 7.2 Any series production craft with a hull made of fibreglass reinforced plastic {FRP} and with a V-hull shape meeting the dimensional and weight characteristics as specified in Table 4 may be used as a standard craft. Table 4 - Specifications of the "Standard craft" Declared propeller shaft power (according to ISO8665) of the outboard motor under test (kw) Length of hull (according to ISO 8666) (m) Beam (according to ISO 8666) (m) Weight without engine (kg) P<6 4,0 1, P<25 4,2 1, P<55 5,0 1, P<150 5,5 2,2 750 P 150 7,0 2, ICOMIA /12

13 @ ICOMIA 1994 A variation of ±10% is allowed in the dimensional characteristics and a variation of ±20% is allowed in the weight of the craft. In addition the craft shall have no covers over the outboard motor or unusual extensions behind the transom which could affect the sound level. ICOMIA /13