Sound of electric motors: examples

This section of e-NVH Academy contains sound files related to Electromagnetically-excited Noise, Vibration, Harshness in electrical machines, focusing on applications where electromagnetic noise is significant compared to aerodynamic and mechanical sources.

Noise of a traction induction machine under sinusoidal supply

Sound of a traction induction machine during run-up under sinusoidal supply

This sound file illustrates acoustic noise observed during the run-up of a squirrel cage induction machine for railway traction application, when fed by a sinusoidal voltage source (no effect of Pulse Width Modulation). High pitch, whining noise comes from slotting effects.

Noise of a traction synchronous motor

Sound of a traction synchronous machine during run-up

This sound file illustrates acoustic noise experienced during a subway starting phase. Noise and resonances are due to electromagnetic excitation of the traction motor, an outer rotor permanent magnet synchronous machine (PMSM).

Noise of a traction machine with PWM

Sound of a DC traction motor during braking phase with changes of PWM strategy

This sound file illustrates acoustic noise experienced during braking phase of a subway. One can observe discontinuous changes of the main noise frequency, which shows that noise is driven by Pulse Width Modulation effects (change of the synchronous switching frequency according to converter strategy).

Noise of a Marvin® drone propeller motors

Sound of UAV propeller motors (quadcopter without blades)

This sound file illustrates acoustic noise experienced during acceleration of the four quadcopter propeller motors without blades. The electric motors are high speed BLDC outrunner motors (outer rotor) with 12 stator slots and 7 pole pairs. As blades have been removed the aerodynamic noise is cancelled and one can see that the electromagnetically-excited noise is significant.

Noise of a Brose® desk motor from Ikea®

Sound of a lifting desk electric motor

This sound file illustrates acoustic noise experienced during the lift of a desk with electric motor. One can observe tones due to electromagnetically-excited noise and gearbox noise. The modulation of these tones is due to low frequency vibration response of the desk.

Noise of a Makita® hand power tool

Sound of Makita<sup>®</sup> driller electric powertrain at no load

This sound file illustrates acoustic noise experienced during the run-up of a brushless cordless drill. One can observe tonal noise at low speed due to Pulse Width Modulation. The synchronous switching frequency changes with driller speed. At higher rotational speed, the PWM noise is masked by the mechanical noise of the driller.

Noise of a Bosch® hand power tool

Sound of Bosch<sup>®</sup> driller electric powertrain at no load

This sound file illustrates acoustic noise experienced during the run-up of a driller. One can observe high frequency tonal noise at low speed due to Pulse Width Modulation. The synchronous switching frequency does not change with driller speed. At higher rotational speed, the PWM noise is masked by the mechanical noise of the driller.

Noise of a Bosch® induction cooking top

Run of an induction cook top

This sound file illustrates acoustic noise experienced during the run of an induction cook top. One can observe frequency tonal noise at 100 Hz and 500 Hz.

Noise of a Braun® toothbrush

Run of toothbrush

This sound file illustrates acoustic noise experienced during the run of a toothbrush. One can observe tonal noise due to electrical motor and mechanical coupling.

Noise of e-bikes
Sound of electric powertrain of Scott® "syncros" moutain e-bike
Sound of electric powertrain of Scott® "syncros" moutain e-bike
Sound of electric powertrain of Scott® "e-sub" urban e-bike
Sound of electric powertrain of Scott® "e-sub" urban e-bike
Sound of electric powertrain of Wayscral® urban e-bike
Sound of electric powertrain of Wayscral® urban e-bike

These sound files illustrate acoustic noise experienced during the run-up of e-bikes: mountain e-bike, hybrid e-bicycle and e-bike at maximum power mode. One can observe high frequency tonal noise due to Pulse Width Modulation for the two first signals. The synchronous switching frequency changes with bikes speed. For the third signal, one can observe tonal noise due to electrical motor with frequency increasing with bike speed.

Noise of e-motion systems
Sound measured on a two-wheeled self balancing unicyle from InMotion<sup>®</sup> during run-up
Sound measured on a two-wheeled self balancing unicyle from InMotion® during run-up
Sound measured on a self balancing unicyle from InMotion<sup>®</sup> during run-up
Sound measured on a self balancing unicyle from InMotion® during run-up
Sound measured on a self balancing scooter from Segway<sup>®</sup> during run-up
Sound measured on a self balancing scooter from Segway® during run-up

These sound files illustrate acoustic noise experienced during the run-up and run-down of e-motion systems: 2-wheels, Inmotion® 1-wheel and Segway®. One can observe high frequency tonal noise due to Pulse Width Modulation and tonal noise due to electrical motor. The synchronous switching frequency and tonal noise due to electrical motor change with e-motion system speed.

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