Wattage as it relates to Loudness in Speakers


I chose this project because I noticed how often I had been using my speaker for activities on campus. More often than not, my flat mates would use it to enjoy some music while making dinner, or I would be tasked with supplying the music for a party. Either way, I saw that I was getting a considerable amount of mileage out of my speaker, and became interested to see how much electricity I was drawing with such a loud yet compact machine. My project sought to determine the loudness, measured in decibels, and power consumption, measured in watts, of my speaker and how power consumption is affected as the speaker outputs music at louder volumes. To do this, I used equipment to measure the wattage of my speaker, and a phone app to record the decibels produced. I used a standardized sound clip to make sure the data was consistent across all trials, with each trial being a different level of volume.

Data Interpretation

The graphs were made in Excel using data collected. The data for wattage was collected with Logger Pro, obtained through a free demo, and the Watts Up Pro, obtained through the physics department. The data for decibels was collected using an android app called “Sound Meter.” I collected the data through Logger Pro and copied it over to Excel. Each round of data collection consisted of setting the speaker volume at a certain level, then measuring wattage with the Watts Up and decibels with Sound Meter as I played the first 10 seconds of “Day & Night” by Thundercat. I chose a short song in case I wanted to play through its entirety. The data shows a steady increase for both decibels and watts, however this increase is much smaller than I originally thought. It seems the speaker is able to efficiently use power, as louder volumes increase the wattage very little. Throughout the experiment, the difference between the lowest and highest wattage used is less than 1 complete unit(not counting when the speaker is off). As for decibels, although there was a consistent increase as volume increased, the data stayed in the same general area for each of the measurements for min, average, and max dB. Upon further research I discovered that decibels are a logarithmic unit. Because of this, loudness is not measured in a linear manner. For example, an increase of 10 decibels would mean that a sound is now twice as loud as before.


After researching electricity providers in the Poughkeepsie area, I was able to determine that electricity sells for about $0.073 cents a kWh. I did some calculations using these numbers to interpret the difference in cost from electricity use in playing my speaker at different volumes. Because the difference in wattage and decibels between individual levels of volume is so incrementally small, I found it more illuminating and satisfying to simply use the measurements of the highest and lowest(without being off) volumes. The highest volume had an average loudness of 80 db, with an average power use of 6.29 watts. The lowest level had measurements of 50 dB and 6.08 watts, respectively. In order to have rounder and more intuitive figures, I scaled up the time in the following measurements from 10 seconds to 1 month. If I were to play music through my speaker for an entire month at the loudest volume, I would spend $0.33 on electricity. If I did the same at the quietest volume, I would spend $0.319. The difference in loudness between the highest and lowest volume is 30 dB. So, the difference in rate divided by the difference in loudness gives the total cost difference of playing my speaker at different volumes. This comes out to be an increase of $0.0007 per 1 dB increase.


I learned during the course of the experiment the scaling of loudness when measuring in decibels. Since most of the exposure to measurement units we have in our everyday life is linear, it’s a bit unnerving when encountering a logarithmic unit. In relation to current science, it’s interesting to see how the electronics we use everyday consume power. There’s push for energy policy changes and understanding how much energy we use and how is an important part of making those decisions. If I had to do this project, I would invest in a better loudness measuring device. The app on my phone was accurate enough, but having consistent measuring through a more reliable device would have made data gathering easier. If I had to continue this project for another six weeks, I would test the power consumption over longer periods of time, as well as utilizing other different speakers to see how much power is used by different brands at comparable loudness.

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