Spectrum Analyzer

Please 'Boom' Responsibly As most of you have noticed, the noise ordinances have become much tougher lately. Most of this is due to idiots, yes IDIOTS, who drive through residential areas with their windows down while their system is playing at full power. To make things worse, the music they listen to has all sorts of foul language that's not suitable for small children, (who may be playing outside). There are even a few people, who are even beyond idiot status, that play their systems at full power through residential areas after 10:00 PM (when many people go to bed). I don't believe that this type of behavior is good for the industry. If the fines get too stiff, people will stop buying large systems. If this happens, more people will get out of car audio (who wants a mediocre system). People get interested in things because they're exciting. A deck and four 6.5" speakers are not going to interest many of the younger car audio enthusiasts. If car audio enthusiasts keep annoying more and more people, the fines will keep getting tougher. All of this will only reduce interest in the equipment that fuels the industry. If you want to listen to your system at full volume, get out on the highway where there's little chance of bothering anyone. When you get to a red light, turn it down. If the only thing attractive about you is your 'system', you have some work to do. Bottom line... Think about what you're doing. Think about other people. It's not the end of the world if you have to turn the volume down for a little while.

Spectrum Analyzer (aka: Real Time Analyzer aka: RTA): In an audio system in a perfect world, all frequencies across the audible spectrum would be reproduced at exactly the same level with respect to all other frequencies. To say the least, this is not exactly a perfect world and the car audio environment is even worse. This means that even if you have a speaker system which will produce a perfectly flat response in an anechoic chamber, when it is installed in a vehicle the frequency response will be significantly less than perfect.; A spectrum analyzer (RTA) graphically indicates the level of the audio signal at various (usually predetermined) points. Many of the most popular RTAs are designed to indicate the level of audio at 30-33 different frequencies across the audio spectrum (also known as a 1/3 octave spectrum analyzer). Most of the portable units use LEDs as level indicators but as portable computers are getting more affordable, some people are moving towards PC based units.; The diagram below is a crude representation of what a spectrum analyzer might look like. As you can see, all of the lit LEDs are centered at 0dB. This would indicate that there was no input or the input at each of the frequencies was exactly the same or at least within 1 dB of each other.; The diagram below is more likely what you would see from a system before it was fine tuned. There may be more dips and peaks and they would likely be at different points but this should give you an idea of what you might see.
Range Settings:: Spectrum analyzers have range settings to adjust the sensitivity to the test conditions. The range settings on the following analyzer determines how much signal level it will take to bring the LED indicators to the zero line. In this example the input signal would be the same for each of the range settings. On '95dB' it takes only 95dB of signal to bring the LEDs to zero on the display. On 100dB, it is slightly less sensitive and would take more signal to bring the display to zero dB. It moves down (relative to the 95dB setting) because the signal doesn't have enough energy to move the LEDs to the same level as before. The 105dB setting is even less sensitive. You can see that part of the display has fallen off of the 'screen'. This setting wouldn't be good for the signal we have. We would have to use one of the more sensitive settings to be able to see the entire display.

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