The quality of sound equipment is tested using audio noise measurement. It accomplishes this by determining the amount of noise in any audio recording. The distortion and noise are then removed using a sound weighting system. Radio and television broadcast studios, recording studios, home recording studios, and audio equipment are all used to make these measurements.
The presence of any unwanted sounds in a recording is referred to as noise. Foreground noise can be caused by microphones, amplifiers, speakers, and other recording equipment. Background noise can also be created using sounds as far away as traffic or in-studio sounds like shuffling papers and general audience noises. Not all noises can be detected before or during the recording process. When a recording is played back through the appropriate equipment, audio noise measurement detects these noises.
Because these are the frequencies of the human voice, the human ear is tuned to pick up medium frequencies. As a result, the human ear struggles to detect extremely low and extremely high frequencies. This refers to the comparison of audio noise measurements to a standard sound pressure level, or SPL. The threshold for sound reaching the human ear is considered to be an SPL of 0. The sound of rustling leaves and whispers has an SPL of 10 to 20, whereas a level of 220 is comparable to a person placing his or her head in front of a canon as it fires.
When measuring audio noise, condenser microphones are commonly used. The frequency response of a condenser microphone is wide. A polarized diaphragm is also included. The free field microphone, the pressure microphone, and the random incidence microphone are the three basic types of condenser microphones used to capture noise.
The presence of noise in recordings can be measured in a variety of ways. Taking a recording of the source of the sound and then a recording of just the background noise is one simple method. The root mean square (RMS) of the energy of all sounds, excluding harmonics, is measured using decibels in signal-to-noise ratio. Harmonics are included in the signal-to-noise plus distortion ratio, whereas the dynamic range measurement compares the greatest magnitude to the quietest signal.
Sound weighting is a technique for removing noises that are audible to the human ear from an audio sound measurement. A-weighting and ITU-R 468 weighting are the two most common weighting methods. An equal-loudness contour is used to create the A-weighting curve, which shows which sounds the human ear is sensitive to. The British Broadcasting Corporation (BBC) created the ITU-R 468 curve, which includes 11 decibels of noise reduction, in response to criticism of the a-weighting curve’s accuracy.