We often hear about dB and dBA’s, but what’s the difference?
A decibel is a unit of measurement of sound level, sound intensity, and sound pressure level. The scale used is not linear, but logarithmic. If the sound pressure level is increased by 10 dB, the human ear will assume that the volume has doubled, if it is reduced by 10 dB, it means that the volume has been cut in half.
The logarithmic addition of the sound levels, by octave bands, makes it possible to obtain the overall level of noise in decibels. Thus, noise is identified by a single number, which by definition does not allow the quantification of low, medium, and high frequencies.
For this reason, the overall level in dB is rarely used, resulting in dB (A), a weighted value that takes into account the corresponding values of the same sound sensation as the human hearing aid.
For the measurement of the sound level, it is typically used a device called sonometer, which through (A, B, and C), simulatesthe behaviour of the human ear. Filter A corresponds to low levels (40 dB),filter B to medium levels (55 to 85 dB), and filter C to high levels (more than 85 dB). Currently, only dB(A) is used for noise analysis, as this is the most extensive filter for the octave bands.
What is a sonometer/ sound level meter?
HANNAIK uses a device to perform acoustic measurements. The word “acoustic” means “sound that travels through the air”. This is opposite to the word “audio”, a term that is also often used in the field of sound measurement. “Audio” refers to a sound that travels electronically through cables and audio components.
A sound level meter needs a microphone to measure the pressure air changes produced by the sound source. The better for the microphone quality, the more accurate the measurements will be. Such measuring microphones are categorized as either Class 1 or Class 2, depending on their measurement accuracy. Whatever the mike is used, it is important for precision that the microphone is well-tuned.
The human ear is a sophisticated sound sensor that encodes the information contained in sound to be interpreted in the brain. The decibel or dB is the unit of measurement used to quantify the sound intensity. Sound can be objectively quantified by measuring the sound pressure level (NPS) using specific equipment already mentioned. The human ear is not equally sensitive at all sound frequencies, it is more sensitive in the range between 2000 Hz and 5000 Hz and less sensitive at extremely low and high frequencies. Due to this fact, the dBA scale was created,which takes into consideration several factors modelling the behaviour of the human ear in a standardized way. Thus, it is possible to estimate the sound pressure level of the human ear.
E.g.: For a sound of 70 dB at 1000 Hz, the human ear fully perceives 70 dBA, however, if the frequency level drops to 50 Hz the human ear will perceive 40 dBA (Figure 2).
In Figure 3 below, it is possible to see the common Sound Level values in dBAvs sound pressure in Pascal (Pa).
HANNAIK always uses the sound level meter to record the dBA’s of each piece of equipment before it leaves the factory to ensure that they meet the required values.
