An interesting thought
Last night I sat chilling in my room with the music playing aloud. I was enjoying my music and increased the volume. The battery on the speaker was blinking red indicating that it was going to run out unless I charge it. It noticeably got quieter and I thought to myself “hmmm does the amount of power or voltage determine how loud the speaker can get?” That thought then led me to think about my project and specifically the piezo speaker. I immediately went on to my laptop to conduct some research. In this blog post I will share my findings and my thoughts on how it may help me on my project.
Before jumping into how loudness is related to power, lets stick to the basics first. What is loudness, power and how is sound actually produced in a speaker is important to understand as it will give us an understanding to how power or voltage may be linked to it.
Power and Voltage
Power in this case is referred as watts. Watts are the units of measure we Voltage is the pressure from an electrical circuit’s power source that pushes charged electrons (current) through a conducting loop, enabling them to do work such as illuminating a light.
Put simply, loudness is the level or intensity of sound. It is measured in decibels or dB. It uses a logarithmic scale meaning it is the inverse function to exponentiation. In laymen terms when it comes to adding loudness level you must use a mathematical equation in order to get the right answer. Decibels cannot be added together .
A loudspeaker produces sound through converting electrical signals into sound waves in the following way. A current within in the coil create a magnetic field which interacts with the permanent magnet generating a force, which then pushes the cone outwards. The current in the cone is meant to flow in the opposite direction. The direction of the magnetic field reverses and the force of the cone then pulls it back in. The repeatedly alternating current direction makes the cone vibrate in and out and these vibrations cause pressure variations in the air. Hence sound is produced. It is important to know that to make loudspeaker cone vibrate correctly, the electric current must vary in the same way as the desired sound.
Now that we know how sound is produced in a loudspeaker we can come up with the conclusion that loudness is related to power and voltage. (When I was at this stage of research I became more intrigued because I had realized that this newfound knowledge was going to affect the project in some way). It was then the time to find out how loudness is related to power and voltage. Here is what I found.
Loudness and its relation to voltage and power
This chart below represents the relationship between all the terms we had previously discussed.
Here we can see on the chart that there is no consistent increase between any of the different units. From what we can conclude here is that to get a doubling of loudness, an increase of 10dB is necessary. Furthermore, to reproduce that volume through the loudspeakers in the first place, would require ten times more power from the amplifier.
Overall I am very happy with my findings as it answered many of my previous questions I had in mind before beginning the project. The main takeaway from this for me is now I understand why my piezo speaker may not produce a lot of sound in comparison to a normal PA system. I may also improve my second version with the thought that I can improve the speakers in mind.