The United States, the world's biggest oil consuming country, consumed 18.5 million barrels of oil per day (mbd) in 2012, which accounted for nearly 20% of the world's total oil consumption per day. The highest level of oil consumption in US history was 20.8mbd, which occurred in 2005.
It is also important to be conscious of the speakerâs sensitivity rating, measured in decibels (dB). The higher the number, the less power a speaker requires in order to reach higher volumes without distortion. For most car speakers, this number typically ranges between 88 to 92 dB.
The tighter the variance, the more flat, or accurate, a speaker's response. Typical variances range from +/- .5 dB to +/- 3 dB, with the lower figure usually bounding the frequency extremes. That is, a speaker whose published frequency response is 50-25 kHz, +/- 3 dB, will be -3 dB below flat at 50 Hz and 25 kHz. This doesn't mean that information below 50 Hz will not be heard, only that the drop-off after that point may be steep.