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Microphones and Acoustics

Frequently Asked Questions

Get your most commonly asked acoustics questions answered.

Section I: Definitions and Terminology
Section II: Microphone Recommendations
Section III: Calibration and Testing
Section IV: Specification Clarifications
Section V: Specialty Microphone Applications
Section VI: Maintenance and Handling

If you don’t see the answer to your question, call our 24/7 SensorLineSM 716-684-0001 to speak with an application engineer or visit Ask the Acoustics Experts.

What is an a-weighted filter?

A-weight is a filtered output signal that simulates how a human ear perceives a sound pressure level at low to intermediate amplitudes, concerning different frequencies.

Many condenser microphone applications involve either designing products to be:

  • More pleasing to the human ear
  • To assess the effects that sound has on the human ear to help preserve hearing

The human hearing range for a newborn with great hearing is 20 Hz to 20 kHz. The hearing range changes as we get older, especially in the upper frequency, when our hair follicles in the ear’s cochlea become damaged.

Within this 20 Hz to 20 kHz range, the human ear perceives sound differently depending upon the frequency and the loudness of the signal. In order to understand how sound is perceived by the ear, Fletcher and Munson performed a study in 1933. The equal loudness curves that they generated were performed to show the relationship between a measured sound and a perceived sound. Points were plotted to represent how loud a sound pressure level would have to be in decibels at different frequencies in order to equal that of a 1 kHz sound at the same loudness level in phons (loudness units of measure.) Through tests like this we learned that the human ear is most sensitive at frequencies between 1 kHz and 6 kHz and naturally attenuates sound at other frequencies.

ANSI incorporated this data into the S1.4 standard for sound level meters. Separate frequency weighting systems were established through the years. The IEC 61052 standard contained: A, B, C and D weighting. The A-weighting was established to represent how the human ear would perceive sound at low levels, 40 phons. Testing also verified that the human ear does not attenuate the sound as much when low frequencies are combined with higher pressure levels. The B, C and D weightings, are based on higher pressure levels. Examples of higher SPL applications include engine noise, gunshot testing, blast detection or aircraft noise.

In 2003 IEC 61672 discontinued the use of the B and D weighting designations and added The Z weighting scale designation which represented a flat or linear unweighted scale. Today’s higher quality sound level meters contain the A, C and linear (Z) weighting data, shown above.

In the above diagram a 100 dB a low amplitude sound pressure level at 100 Hz will be attenuated approximately 20 dB. So the human ear will perceive that 100 dB signal as 80 dB (less loud.)

Understanding how the human ear perceives their products is highly desirable by consumer goods manufacturers who want to make a product more pleasing to the ear and will commonly use an A-Wt output. Some of the popular companies that use A-Wt are White goods manufacturers for appliances (dishwashers and washing machines, air conditioning units, etc), hand tools (grinders, jackhammers, drills, etc), computers, environmental studies and cabin noise for auto and aerospace manufacturers.

What is an a-weighted filter?

A-weight is a filtered output signal that simulates how a human ear perceives a sound pressure level at low to intermediate amplitudes, concerning different frequencies.

Many condenser microphone applications involve either designing products to be:

  • More pleasing to the human ear
  • To assess the effects that sound has on the human ear to help preserve hearing

The human hearing range for a newborn with great hearing is 20 Hz to 20 kHz. The hearing range changes as we get older, especially in the upper frequency, when our hair follicles in the ear’s cochlea become damaged.

Within this 20 Hz to 20 kHz range, the human ear perceives sound differently depending upon the frequency and the loudness of the signal. In order to understand how sound is perceived by the ear, Fletcher and Munson performed a study in 1933. The equal loudness curves that they generated were performed to show the relationship between a measured sound and a perceived sound. Points were plotted to represent how loud a sound pressure level would have to be in decibels at different frequencies in order to equal that of a 1 kHz sound at the same loudness level in phons (loudness units of measure.) Through tests like this we learned that the human ear is most sensitive at frequencies between 1 kHz and 6 kHz and naturally attenuates sound at other frequencies.

ANSI incorporated this data into the S1.4 standard for sound level meters. Separate frequency weighting systems were established through the years. The IEC 61052 standard contained: A, B, C and D weighting. The A-weighting was established to represent how the human ear would perceive sound at low levels, 40 phons. Testing also verified that the human ear does not attenuate the sound as much when low frequencies are combined with higher pressure levels. The B, C and D weightings, are based on higher pressure levels. Examples of higher SPL applications include engine noise, gunshot testing, blast detection or aircraft noise.

In 2003 IEC 61672 discontinued the use of the B and D weighting designations and added The Z weighting scale designation which represented a flat or linear unweighted scale. Today’s higher quality sound level meters contain the A, C and linear (Z) weighting data, shown above.

In the above diagram a 100 dB a low amplitude sound pressure level at 100 Hz will be attenuated approximately 20 dB. So the human ear will perceive that 100 dB signal as 80 dB (less loud.)

Understanding how the human ear perceives their products is highly desirable by consumer goods manufacturers who want to make a product more pleasing to the ear and will commonly use an A-Wt output. Some of the popular companies that use A-Wt are White goods manufacturers for appliances (dishwashers and washing machines, air conditioning units, etc), hand tools (grinders, jackhammers, drills, etc), computers, environmental studies and cabin noise for auto and aerospace manufacturers.