Leaf Blower Noise

LEAF BLOWER NOISE Teemu Pasanen Esko Rytkönen Esko Sorainen Kuopio Regional Institute of Occupational Health Acoustics Laboratory P.O.B 93, FIN-70701 Kuopio, Finland Teemu.Pasanen@ttl.fi ABSTRACT Acoustics laboratory of Kuopio Regional Institute of Occupational Health examined noise of leaf blowers and other professional gardening and municipal machines. Noise emission and noise exposure of users was measured. In total of 9 leaf blowers were tested. Noise emission data of leaf blowers were compared with noise data from other gardening machines. Noise exposure of leaf blower users varied between 93-102 dB(A). Highest noise exposures were measured with machines powered by 2-stroke engines, e.g. leaf blowers and brush cutters. Noise emissions of leaf blowers varied between 102-111 dB(A). Only lawn mowers noise emission was less than 100 dB(A). Especially noise of machines powered by 2-stroke engines included tonal components. Tonal components of noise are perceived more irritating. Penetration of gardening machine noise to indoors was calculated. Low frequency components of noise from leaf blowers engine penetrate outer wall constructions well. Transportation of noise through wall also increases relative importance of low frequency tonal components of leaf blower noise. 1. INTRODUCTION Noise from leaf blowers is often described very loud and irritating. Every year at spring and autumn time many letters to the editor complaining noise of leaf blowers can be read in the newspapers. Acoustics laboratory of Kuopio Regional Institute of Occupational Health examined noise of leaf blowers and other professional gardening and municipal machines. 2. MATERIALS AND METHODS Machine types tested were leaf blower, brush cutter, grass trimmer, lawn mower, snow blower, garden tractor with lawn mowing equipment and two types of sweeping machines. All the machines tested were used. Leaf blowers were 1 to 7 years old and other machines 2 to 21 years. Eight of the leaf blowers tested were backpack models and one of the leaf blowers was handheld. 2-stroke petrol engines power leaf blowers, brush cutter and grass trimmer. 4 stroke petrol engines power lawn mower and snow blower. Diesel engines power garden tractor and sweeping machines. Garden tractor and sweeping machines are equipped with driver cabins. Noise emissions of machines were tested according to European Directive 2000/14/EC [1]. In this Directive noise emission test method is based on standard EN ISO 3744:1995 [2]. More detailed measurement methods for each type of machines are also laid down in the directive. Joint Baltic-Nordic Acoustics Meeting 2004, 8-10 June 2004, Mariehamn, Åland BNAM2004-1 Hemispherical measurement surface with six microphone positions was used for all machines (figure 1). Noise in microphone positions was recorded using sound level meter and DAT-recorder. In addition, users noise exposure was recorded according to standard ISO 11202 [3]. Recordings were analyzed with real time analyzer in 1/3 octave bands. Test site was lawn for leaf blowers and lawn mowers and asphalt for other machines. Leaf blower noise emission test site and test procedure is presented in figure 2. y z 5 1 5 x r 2 3 3 6 6 1 4 0,71 r r 1,5 2 4 x Figure 1. Hemispherical measurement surface with six microphone positions. Figure 2. Leaf blower noise emission test site. Microphone positions are marked with white buckets. Joint Baltic-Nordic Acoustics Meeting 2004, 8-10 June 2004, Mariehamn, Åland BNAM2004-2 People spend most of their time indoors. Therefore exposure to environmental noise can also occur indoors. Penetration of noise from gardening machines to indoors was calculated using measured noise emission and estimated outer wall transmission loss (figure 3). In calculations it was assumed that machines were used at 10 meters distance from wall. Estimated outer wall transmission loss is based on mass law and measurements made in practical circumstances. Goal of this estimation is to describe sound insulation of typical outer wall construction with windows. dB 60 55 50 45 40 35 30 25 20 15 Hz 5000 4000 3150 2500 2000 1600 1250 800 1000 630 500 400 315 250 200 160 125 100 80 63 50 10 Figure 3. Estimated outer wall transmission loss in 1/3 octave bands. Joint Baltic-Nordic Acoustics Meeting 2004, 8-10 June 2004, Mariehamn, Åland BNAM2004-3 3. RESULTS 3.1. Noise emission and user exposure Noise emission and users noise exposure of the leaf blowers and other gardening and municipal machines are presented in table 1. In the table there is also a figure number pointing to machines noise emission spectrum. Table 1. Noise emission and users noise exposure of the machines tested Machine tested Noise emission Users exposure Noise emission LWA dB(A) LpA dB(A) spectrum 1 Echo PB-6000 leaf blower 109 98 Figure 4 2 Echo PB-6000 leaf blower 108 99 3 Echo PB-4600 leaf blower 106 95 Figure 5 4 Echo PB-4600 leaf blower 106 97 5 Husqvarna 155 B leaf blower 111 100 Figure 6 6 Husqvarna 141 B leaf blower 107 97 Figure 7 7 Husqvarna 141 B leaf blower 107 98 8 Stihl BR 420 leaf blower 110 102 Figure 8 9 Husqvarna 225 BV leaf blower / vacuum 102 93 10 Echo CLS-4600 brush cutter 115 105 Figure 10 11 Echo CLS-4600 grass trimmer 113 104 12 Klippo PRO 4 OHV lawn mover 93 80 Figure 11 13 Toro 421 snow blower 109 92 Figure 12 Wille 345 Park garden tractor 14 107 76 + lawn mowing equipment Bucher Schörling City Cat 2000 15 108 77 Figure 13 sweeping machine Sisu SK 177 / Schörling sweeping 16 114 71 machine Noise exposure of leaf blower users varied between 93-102 dB(A). Highest noise exposures were measured with machines powered by 2-stroke engines. Noise emissions of leaf blowers varied between 102-111 dB(A). The leaf blower with highest rated engine power was also noisiest. Lowest noise emission of the leaf blowers was from Husqvarna 225 BV leaf blower / vacuum. This machine is handheld and not powerful enough for professional use. Only lawn mowers noise emission was less than 100 dB(A). Joint Baltic-Nordic Acoustics Meeting 2004, 8-10 June 2004, Mariehamn, Åland BNAM2004-4 3.2. Spectrum analyzes 110 dB(A) 120 110 90 100 80 70 60 50 A-weighted 1/3 octave sound power level spectrums of selected machines are presented in figures 4-13. dB(A) 100 dB(A) 100 90 120 90 80 120 80 70 109 70 60 110 60 Hz Hz 120 dB(A) 110 100 90 80 70 60 50 50 Figure 5. Echo 4600 leaf blower 25 31,5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 12500 16000 20000 dB(A) 50 Figure 4. Echo 6000 leaf blower 25 31,5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 12500 16000 20000 dB(A) 111 107 102 106 Figure 7. Husqvarna 141 B leaf blower dB(A) 120 110 100 90 80 70 Figure 6. Husqvarna 155 B leaf blower 110 25 31,5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 12500 16000 20000 dB(A) 60 50 dB(A) 120 110 100 90 80 70 25 31,5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 12500 16000 20000 dB(A) Hz Hz Hz Hz 25 31,5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 12500 16000 20000 dB(A) 60 50 Figure 9. Husqvarna 225 BV leaf blower / vacuum BNAM2004-5 Figure 8. Stihl BR 420 leaf blower Joint Baltic-Nordic Acoustics Meeting 2004, 8-10 June 2004, Mariehamn, Åland 25 31,5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 12500 16000 20000 dB(A) dB(A) 120 dB(A) 120 115 110 110 100 100 90 90 80 80 70 70 60 60 50 93 25 31,5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 12500 16000 20000 dB(A) 25 31,5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 12500 16000 20000 dB(A) 50 Hz Figure 10. Echo 4600 brush cutter Figure 11. Klippo Pro 4 OHV lawn mower dB(A) 120 dB(A) 120 Hz 108 109 110 110 100 100 90 90 80 80 70 70 60 60 50 25 31,5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 12500 16000 20000 dB(A) 25 31,5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 12500 16000 20000 dB(A) 50 Hz Figure 12. Toro 421 snow blower Hz Figure 13. Bucher Schörling City Cat 2000 sweeping machine 3.3. Calculated noise penetration to indoors Calculated A-weighted spectrums of noise penetrated to indoors are presented in figures 14-17. Calculations were made with two leaf blowers, lawn mower and snow blower noise. dB(A) dB(A) 50 50 44 45 45 40 40 35 35 30 30 25 25 20 20 41 15 Figure 14. Husqvarna 155 B leaf blower Hz 5000 dB(A) 3150 4000 2500 1600 2000 1250 800 1000 630 500 315 400 250 160 200 125 10 80 100 dB(A) 3150 4000 5000 2000 2500 1000 1250 1600 630 800 400 500 200 250 315 125 160 63 80 100 50 10 63 Hz 50 15 Figure 15. Stihl BR 420 leaf blower Joint Baltic-Nordic Acoustics Meeting 2004, 8-10 June 2004, Mariehamn, Åland BNAM2004-6 dB(A) dB(A) 50 50 45 45 40 40 35 37 35 27 30 30 25 25 20 20 15 15 5000 dB(A) 4000 3150 2000 2500 1600 1250 800 1000 500 630 400 315 250 160 200 125 80 Figure 16. Klippo Pro 4 OHV lawn mower 100 63 5000 dB(A) 3150 4000 2500 1600 2000 1250 800 1000 630 500 315 400 250 160 200 125 80 100 63 50 Hz 10 50 Hz 10 Figure 12. Toro 421 snow blower 4. CONCLUSIONS The engine power of the leaf blowers seems to contribute more to noise emission than other parameters. The noise of machines powered by 2-stroke engines includes tonal components in the low frequency area (figures 4-10). These tonal components are in the frequency area equivalent to engine speed of the machines. Tonal components of noise are perceived more irritating. Low frequency components of noise from leaf blowers engine penetrate outer wall constructions well. Transportation of noise through wall also increases relative importance of low frequency tonal components of leaf blower noise. This filtration of leaf blower noise through outer wall seems to make it more irritable. This may partly explain the strong public reaction to leaf blower use. 5. REFERENCES [1] DIRECTIVE 2000/14/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 8 May 2000 on the approximation of the laws of the Member States relating to the noise emission in the environment by equipment for use outdoors. Official Journal of the European Communities. L162/1. 3.7.2000. [2] ISO 3744:1994 Acoustics – Determination of sound power levels of noise sources using sound pressure – Engineering method, International Organization for Standardization (ISO), Geneva, 1994. [3] ISO 11202:1995 Acoustics – Noise emitted by machinery and equipment – Measurement of emission sound pressure levels at a work station and other specified positions – Survey method in situ; International Organization for Standardization (ISO), Geneva, 1995. Joint Baltic-Nordic Acoustics Meeting 2004, 8-10 June 2004, Mariehamn, Åland BNAM2004-7