|Sound Pressure and Distance
As there are differences in the measuring distances when manufacturers make the measurement of sound pressure, the following formula is recommended for calculation on occasions when a buzzer itself is tested or compared with a planned finished product. However, as far as the calculated value is concerned, it is theretical one and therefore subject to change, depending upon circumstances and conditions.
The formula is:
B=A+20 log (La/Lb)—A :Sound Pressure Value at distance La Ex.When the distance is doubled—B : Sound Pressure Value at distance Lb
B=A+20 log (la/Lb)=A+20 log (1/2) =A – 6.02 i.e. the sound pressure is apt to be reduced by 6.02 dB.
The table below is to shape up relations between the measuring distance variation and the sound pressure variation for reference.
The tone output, generated by buzzers, is essential in product design. A recommended way of selecting a desired tone is by listening to the different tones produced by the different buzzer. Additionaly, FFT analysis is usable for visual tone selection method. The sound is not an oscillation of a single frequency, but as a collected body of individual frequencies. The analysis is to diagnose the ratio of constituent frequencies. The following is a sample analysis of our typical buzzers.
Element with Feedback Tab
This type of element has a tab form on the ceramic part. It used as the feedback function in a simple oscillation circuit , it will create a back voltage , or back EMF. to the internal circuit . Thus, the element operates automatically at the natural resonant frequency of the element and the loudness sound can be obtained.
Edge Mounting (External Drive Usage)
To fix the edge of the element to the supporting ring of the case. SPL depends on input frequency. However, considerable sound pressure can be obtained covering a wide frequency range around the resonant frequency.
Nodal Mounting (Self Drive Usage )
To fix the nodal diameter of the element to the supporting ring of the case. Loud sound pressure can be obtained at the resonant frequency. The SPL will drastically drop when the frequency is not at resonant point. This is the high efficient type of mounting for feedback type element.
Mounting Method for Sound Element