10. How to increase SPL?
(1) Decrease the distance
SPL increases when distance from sound source decreases. Based on acoustic formula1, when clients reduce the distance from source by half, they get an SPL increase by 6dB.
(2) Increase the input power
SPL increases when input power increases. Based on acoustic formula2, when clients double input power, for example by raising voltage input, they get an SPL increase of 3dB.
(3) Make sound waves reflect
Theoretically placing baffles around the sound source will yield SPL increase ranging from 6dB to 18dB3. But practically due to violations of theoretical assumptions, SPL increase varies. The principle is that baffles reflect and concentrate sound waves, elevating its intensity thus raising SPL. Putting the sound source in an enclosed or vented box renders similar effects. Our team is delighted to advise clients on mechanical design surround our acoustic products to improve reflection and resonation.
(4) Enlarge the diaphragm
The larger the diaphragm, the more air it propels, and the higher the SPL becomes
(5) Intensify the vibration force
The following methods can be applied in the R&D stage, but is inexecutable after the product is made. For micro-speakers, receivers and magnetic buzzers, one can add more coil, replace with better magnet, or optimize magnetic circuit to elevate the electromagnetic force. For piezo buzzers, one can choose crystals with better piezoelectric response. Other methods include choose appropriate material of diaphragms or changing how the diaphragms are fixed.
(6) Emit sound at resonant frequency
Every acoustic component corresponds to a resonant frequency, at which the component emits the loudest sound. This frequency changes as the component is mounted in your final products. AATC helps to measure the resonant frequency for you, and suggests you to give out sound around this frequency.
Footnotes:
1. Sound pressure is inversely proportional to distance from sound source. And the relationship between SPL and sound pressure is logarithmic. When distance is reduced by half, sound pressure will be doubled. SPL increase is given by 20*log(2) dB, approximately 6dB.
2. Sound power is inversely proportional to distance square. According to footnote 1, we deduct that as input power doubles, sound pressures becomes “square root of two” times its original value. Thus SPL increase is given by 20*log(2^(1/2)) dB, approximately 3dB.
3. Consider a speaker hovers in a large free field. If clients put a large baffle behind the speaker, theoretically the SPL increase will approach 6dB; If clients first position two large baffles so that the angle between them is 90 degrees, and then put the speaker in between two baffles, theoretically the SPL increase will approach 12dB; If clients arrange three baffles together than resembles a corner, and then place the speaker right in the corner, theoretically the SPL increase will approach 18dB.
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