What is the relationship between motor sound and noise? Introducing causes and countermeasures

• 

  Noise...

• 

  What is it, Vex?

• 

  I was consulted by a customer. The content of the question, which was for equipment that uses a stepper motor, "If the vibration of the motor is resonating with the equipment or enclosure and causing noise, what measures can be taken?" I'm not sure how to answer this question... People have different perceptions, and noise tends to be a sensory thing.

• 

  It's difficult to take the senses into account. But we can also describe the noise without relying on our senses. First, let's clarify the relationship between sound and noise. Sound is made up of three elements: loudness (sound pressure), height (frequency), and timbre (sound waveform).

• 

  The vibration of the equipment should be transmitted to the air and heard as sound, right?

• 

  That’s right. In equipment, the vibration depends on the material, rigidity, and size of the parts, and the larger the vibration, the louder the sound will be heard.

• 

  Noise is annoying and unpleasant sound among them. What generally causes discomfort?

• 

  The main factors of discomfort are "sound pressure" and "frequency." Sound pressure can be measured with a noise meter, and when it exceeds 70 dB, you start to feel anxious, and the louder it gets, the more it affects your body.

  

• 

  It's true that if a loud sound keeps coming from a speaker nearby, I can't stand it and leave the place or turn down the volume. But there are times when you feel uncomfortable, even when the sound is not so loud.

• 

  That's right. That's because of the other element of noise "frequency". Frequencies that are high in the human audible range cause discomfort, like tinnitus. In particular, the sound of mosquitoes flying around is known as the mosquito sound.

  

  On the other hand, low frequency sounds that are inaudible to the human ear are also known to cause discomfort and pressure to people. Low frequencies are most likely to be generated by large machines such as blowers and pumps.

• 

  Come to think of it, the mosquito sound is used as an ear age test because as we get older, it becomes difficult to hear the high pitched sounds.

• 

  In addition, recent studies have shown that humans are sensitive to a certain range of sounds, such as scratching a blackboard, from 2 k to 5 kHz. So for less loud noises, the key is not only to reduce the sound pressure, but also to avoid the frequency bands that are uncomfortable. How is it? Do you understand the relationship between sound elements and noise now?
  Based on what you've just said, Vex, what kind of noise control measures would you propose to your customers?

• 

  First of all...I will tell that if you have enough torque, you can reduce the amplitude of the vibration and the sound pressure by reducing the operating current of the motor. Next, we propose to shift the resonance frequency by changing the rotation speed of the motor to avoid sounds in frequency bands that are uncomfortable.

  

  Other things I would like to introduce are...reinforcing the rigidity of the mounting surface of the enclosure, and anti-vibration rubber and dampers to absorb vibrations.

• 

  As expected! But if their equipment is still in the evaluation stage, you should definitely recommend the CVD Series! We have achieved low vibration and low noise with it by reviewing the motor winding design and developing a dedicated driver IC. It is being used by many people who are looking for quietness and low vibration.

  

  Anyway, it's low vibration and quiet. Watch the video and listen to the sound!

  Comparison video of typical motor and low-vibration, quiet motor drive noise

  

• 

  I was really surprised.
  I can feel that the 35 dB of the 5-phase CVD Series is really quiet. I will show it to the customer as soon as possible.

Related Products

View More About the Stepper Motors PKP Series/CVD Series Pulse Input Drivers

Stepper Motors PKP Series/CVD Series Pulse Input Driver

View More about Stepper Motors PKP Series/CVD Series RS-485 Communication Type Driver

Stepper Motors PKP Series/CVD Series RS-485 Communication Type Driver