Car Audio Testing

I decided to do test out the sound levels in the car with 400 amp and sub woofer in place. I bought a sound mter from Radio Shack to carry out the tests. The first order of business was to determine the read sound levels in the car both at rest and in motion. I did sound level readings with the car stopped. I got the following reading. 51dB.
I then took readings with the car in motion. I took the car up to 90 kph (50 mph) to get these readings. I factored in the readings with the windows closed and open. I got these reading.
Sound level with windows closed- 65dB
Sound level with windows open- 76dB
My test base for the music was a taped CD of AC/DC, Back in Black on a chrome tape.
Besides the Kenwood sub and 400 watt amp, my stereo uses a Pioneer 35 watt by 4 KEN-1500 AM/ FM head unit and 4, 6" 100 watt speakers in there factory locations. I used three locations for doing the sound tests. I placed the meter on the front passenger seat, the middle of the rear passenger seat and at the rear of the car, 12" inches away from 10" sub speaker with the hatchback open. For the interior tests, I placed the meter on a small pocket tripod.
All volume readings are what is seen on the head units display readout.
The following settings where used in the balancing of the system. Bass was set at 0. Trebel was set at plus2. The display for the front/ rear balance was set at BR:3. The left/ right balance was set-up as BR:3.
Front seat mounting point for sound readings.
Rear seat mounting point for sound readings.
The meter placed on the tropod in it's two interior test locations.
The meter has to settings. The first setting is called the "A" setting. The sound range is from 500mz to 10,000mz. This is recommended for general sound level testing. I used this setting in the base level readings in the base noise levels before the stereo was put on.
The other setting that is on the meter is called "C". This is recommended for any type of music where instruments and voices are used. The sound range in this mode is 32mz to 10,000mz. I used this for tests when the stereo was on.
To see the sound levels compared to the base readings I did, I used the "A" setting to compare the sound levels. This will give me readings that are in the same audio range as the base. The "C" settings readings give out a different level setting as you will see.
The following readings in the "A" setting where attained.
Sound level at 16- 80dB
Sound level at 20- 88dB
Sound level at 22- 94dB
Sound level at 24- 97dB
The following same volume settings in the "C" setting.
Sound level at 16- 90dB
Sound level at 20- 99dB
Sound level at 22- 101dB
Sound level at 24- 109dB
The meter at it's highest setting while a sound test is being done.
The head unit at it's highest test setting. At this volume, it is very uncomfortable as you can see from the sound readings.
This test in this location was done seeing that I spent all the time in car. The readings on the driver side where I sit worked out be basicly the same. Using the passenger seat meant I could take readings both in the stopped and moving car.
The next location to be tested was the rear passenger seat. I rarely use this but seeing that the two rear 6" speakers are part of the audio system and balance out the overall sound, I took reading there. Here are the results. I only used the "C" setting in this location.
Sound level at 16- 93dB
Sound level at 20- 101dB
Sound level at 22- 107dB
Sound level at 24- 111dB
The last test was to open the hatchback and take readings off of the 10" sub speaker. Here are the results. Once again, I only used the "C" setting on the meter.
Sound level at 16- 88dB
Sound level at 20- 93dB
Sound level at 22- 99dB
Sound level at 24- 102dB
I really turned the settings on the amp down so that the sub-woofer in much more balanced place of the overall sound system.
Conclusion
The addition of the sub in the car really balances out the sound system. Although I lacked the meter to do test before the amp and sub, there is a marked difference in the sound quality. I used to set the volume on the head unit at about 26 to 28 with the windows down. I now use between 19 and 22 depending on what type of music is being played. Given some of the high numbers being created at the high end of the volume, the car can become a long term health hazard to your hearing if abused.

NOTE-*Please note all volume reading shown where do in the stopped car. Informal moving testes where done and there was only a small difference in sound levels. Some of the musics sound range in the low end was reduced a bit at speed compared to being at a stopped postion.