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The Genesis of Noise

Alternator noise is a high pitched whine that is synchronous with the car's engine acceleration. When the engine turns the alternator rotor, the alternator induces an AC voltage that is converted to DC and distributed to the electrical system.

It is similar to an inverted electric motor (voltage is created from the motion of rotating and interacting magnetic fields).
While the rectifiers imbedded in the alterntor convert the AC voltage produced by the alternator to DC, there is always a small quantum of residual AC that finds it's way into the power distribution system. The frequency of this AC component changes with the speed of the motor, increasing in pitch with the acceleration. This is why alternator noise is more pronounced in source speakers: mids and tweeters, but less so in woofers, Woofers concentrate on low frequencies, below the frequency of most alternator noise. However, there are a variety of other devices in the electrical system that can also produce noise at various frequencies, like spark plugs and wires, distributors,and AC compressors.

How alternator noise becomes audible

1. Induced noise: When current passes through a wire, an electromagnetic field radiates from it. This field will carry with it all the noise imposed by the system, and any noise created by peripheral devices such as factory harnesses, car computers, navigation and phone systems, and other electronic equipment as well.

Any signal carrying wires - line and speaker cables and wires which are running in parallel to these power wires, are subject to having noise induced and added to the sound signal. This occurs because the audio signal a very low voltage signal, often in the millivolt range . This induced signal will be amplified along with the program.

Repairing this problem is very simple: DO NOT run power and signal wires in close parallel! Never allow power and signal wires to run in parallel closer than 8 inches. When they must cross, try to place them at 90 degree angles perpendicular to each other. Run power wire from the battery to the amp on one side of the vehicle, and the signal wires along the other side of the car. On most cars it is better to run signal wires on the passenger's side, and power wires on the driver's side.

2. Ground loops: The metal chassis and body of the car serves as a ground. If the battery and alternator are under the hood, and an amplifier is connected to the body at the trunk area, it is highly likely that the ground potential may be just a few millivolts off from what it would be at the front or middle section of the same car body. Allthough theoretically, the car's metal has little or no resistance, and it should not matter where grounds are connected for amplifiers, radio, battery and alternator, the metal in the car does have resistance, and there is a potential difference from the front of the car, where the battery is, to the middle of the car, where the radio is, and the back of the car, where most amplifiers are situated. The small difference in electrical potential is sufficient to allow noise to intrude at undesirable levels. Differences of as little as 1/5 volt, can create noise problems.

To treat this problem, make sure that the amplifiers have a good ground first. Use the same gauge wires for the grounds as for the + power. If you have 2 or more amplifiers, DO NOT wire the ground terminal of one amp to the other and then from there to ground as this also promotes noise. Tightly ground each amplifier independently to a clean metal part of the car body. Use a similar approach with stiffening capacitors, go to a separate ground for the cap.

Troubleshooting Tips

If everything is configurred using the above guidelines and you still have noise, then try to figure out what is causing the noise . First, double check all grounds at amplifiers, crossovers, radio, etc. Make sure the antenna is well grounded. Try to isolate the source of the noise. Bypass crossovers, signal processors, equalizers, etc, by connecting RCA cables straight from the radio to the amplifier. If the noise goes away, this is an indication the problem may be RCA wires or grounds hooked up to crossovers/equalizers.
If you have more that one amplifier and have noise only on one amplifier try switching RCA cables around. If noise stays the same, then problem is the amplifier, if it switches, noise is coming from previous components up the line. As said before, it is very hard to find out what is causing alternator noise.

Noise filters

Noise filter devices should be considered once you have exhausted all the remedies we suggest above. These usually go in the battery + line. Active filtration is better than a passive filter. For a selection of such filters see our page here. The Ans-80 is one of our most effective and popular models.
In the next to last resort, you might try an audio line filter. But this has the effect of substantially diminishing frequency response and otherwise changing the nature of the signal. Choose your filter carefully, purchase is at your own risk!

If you have tried everything, and still have that annoying noise, contact your nearest car electrial technician.

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Welcome To The Stereo Technical Information Center. We Offer: Stereo Technical Information Of All Kinds, Including: A Glossary Of Technical Terms, Links To Manufacturer's Websites, Information On How Speakers Work, Choosing Speakers, What's A Woofer?, What's A Midrange?, What's A Tweeter?, What Are Dual-Cone/Dual-Voice-Coil/Full Range Speakers?, 2/3/4-Way & Component Speakers, What's A Capacitor?, Installing A Capacitor, What's A Crossover?, What's An Equalizer?, Speaker Enclosures, Power Amps. Installing An Amp, Amp Installation Tips, Understanding Power Ratings, Installing & Replacing Head Units/Receivers, About Theile/Small Parameters, Installing Neon/LED, Eliminating Unwanted Noise, Using The Right Tools, Home Stereo Tech Information, Frequently Asked Questions, Home Stereo Glossary, About Home Speakers & DriversPlus Sales Of Car, Home and Mobile Audio and Stereo, Marine Audio, Technical Information, Amplifiers, Mono Block Amps, Woofers, Speakers, Mid Range, Tweeters, Capacitors, Woofer Boxes, Bandpass, Bass Reflex Enclosures, Woofer Tubes, Receivers, CD Players, MP3, Satellite Radio, CD Changers, Bass Packages, Car Alarms, Remote Starters, Car Security, Keyless Entry, Wiring and Accessories, Antenna Boosters, Antennas, Bass Blockers, Crossovers, Dynamat, Equalizers, Cooling Fans, Noise Filters, Power Inverters, Power Supplies, RCA Cables Splitters, Remotes, Signal Boosters, Speaker Grills, Vibration Control, Wiring, Mobile Video, Personal and Mobile Electronics, Laptops, Cell Phones, PDAs, GPS, Electronic Books/Readers, Kindle, MP3, Earphones/Buds, Blu-Ray, Bluetooth, Calculators, Marine Stereo, Fish Finders, Flat Screen HD TVs, DVD Players, Tivo, DVD Recorders, Surround Sound, Stereo Drivers, Home Speakers, Enclosed Subwoofers, Video Games, Computer Games, Digital Photo Frames, Computers, PCs, Laptops, Monitors, Software, Printers, Scanners, Computer Supplies, Virus Security.




Car Stereo & Electronics Amplifiers Subwoofers Full-Range Speakers Midrange Speakers Tweeters Power Capacitors Empty Enclosures Loaded Enclosures CD/Mp3 Receivers CD Changers Bass Packages Car TV/Video Satellite Radio Bluetooth Wireless GPS Navigation Neon/LED Lighting Radar Detectors Chrome Mufflers Car Alarms/Security AUTO PARTS STORE Auto Wiring & Accessories Air Horns Power Antennas Antenna Boosters A/V Controllers Bass Blockers Crossovers Dynamat Equalizers Fans (Cooling) FM Modulators Interfaces Line Converters Noise Filters Power Inverters Power Supplies RCA Cables RCA Splitters Remote Controls Signal Boosters Vibration Control Speaker Grills Wiring Kits Marine Stereo & Electronics Stereo Amplifiers Stereo Speakers Stereo Woofers Woofer Tubes Enclosed Speakers Wakeboard Speakers CD/Mp3 Receivers TVS & Video VHF Radios GPS Navigation Fish Finders Depth Finders Chart Plotters Accessories Home Stereo & Electronics Flat Screen & HD TVs Surround Sound Home Theater DVD Players/Tivo DVD Recorders Blu-Ray Devices Amplifiers/Tuners Speaker Systems Subwoofer Drivers Midrange Drivers Tweeter Drivers Powered Subwoofers Outdoor Speakers Stereo Accessories Digital Photo Frames Video Game Systems Game Accessories Video Games Home Security/Alarms Computers & Related Products Desktops & Laptops Add-Ons/Peripherals Computer Monitors Computer Software Computer Games Printers & Scanners Ink/Specialty Papers Parts & Components Computer Supplies Security/Tech Support Personal Stereo & Electronics Laptop Computers Cell Phones & PDAs Portable TV & Video Electronic Readers MP3/Music Players CD Players/Booms Earphones/Buds Digital Cameras Video Cameras Personal GPS Bluetooth Calculators Accessories Technical Help & Education Glossary Of Terms Speakers Main Page How Speakers Work Choosing Speakers What's A Woofer? What's A Midrange? What's A Tweeter? Other Speaker Types More Speaker Types What's A Capacitor? Installing A Capacitor What's A Crossover? What's An Equalizer? Speaker Enclosures Theile/Small Param. About Power Amps Installing An Amp Installation Tips Power Ratings Installing/Replacing Head Units/Receivers Installing Neon/LED Eliminating Noise Use The Right Tools Manufacturer's Links Home Stereo Tech Information FAQ Glossary Home Speakers	The Genesis of Noise Alternator noise is a high pitched whine that is synchronous with the car's engine acceleration. When the engine turns the alternator rotor, the alternator induces an AC voltage that is converted to DC and distributed to the electrical system. It is similar to an inverted electric motor (voltage is created from the motion of rotating and interacting magnetic fields). While the rectifiers imbedded in the alterntor convert the AC voltage produced by the alternator to DC, there is always a small quantum of residual AC that finds it's way into the power distribution system. The frequency of this AC component changes with the speed of the motor, increasing in pitch with the acceleration. This is why alternator noise is more pronounced in source speakers: mids and tweeters, but less so in woofers, Woofers concentrate on low frequencies, below the frequency of most alternator noise. However, there are a variety of other devices in the electrical system that can also produce noise at various frequencies, like spark plugs and wires, distributors,and AC compressors. How alternator noise becomes audible 1. Induced noise: When current passes through a wire, an electromagnetic field radiates from it. This field will carry with it all the noise imposed by the system, and any noise created by peripheral devices such as factory harnesses, car computers, navigation and phone systems, and other electronic equipment as well. Any signal carrying wires - line and speaker cables and wires which are running in parallel to these power wires, are subject to having noise induced and added to the sound signal. This occurs because the audio signal a very low voltage signal, often in the millivolt range . This induced signal will be amplified along with the program. Repairing this problem is very simple: DO NOT run power and signal wires in close parallel! Never allow power and signal wires to run in parallel closer than 8 inches. When they must cross, try to place them at 90 degree angles perpendicular to each other. Run power wire from the battery to the amp on one side of the vehicle, and the signal wires along the other side of the car. On most cars it is better to run signal wires on the passenger's side, and power wires on the driver's side. 2. Ground loops: The metal chassis and body of the car serves as a ground. If the battery and alternator are under the hood, and an amplifier is connected to the body at the trunk area, it is highly likely that the ground potential may be just a few millivolts off from what it would be at the front or middle section of the same car body. Allthough theoretically, the car's metal has little or no resistance, and it should not matter where grounds are connected for amplifiers, radio, battery and alternator, the metal in the car does have resistance, and there is a potential difference from the front of the car, where the battery is, to the middle of the car, where the radio is, and the back of the car, where most amplifiers are situated. The small difference in electrical potential is sufficient to allow noise to intrude at undesirable levels. Differences of as little as 1/5 volt, can create noise problems. To treat this problem, make sure that the amplifiers have a good ground first. Use the same gauge wires for the grounds as for the + power. If you have 2 or more amplifiers, DO NOT wire the ground terminal of one amp to the other and then from there to ground as this also promotes noise. Tightly ground each amplifier independently to a clean metal part of the car body. Use a similar approach with stiffening capacitors, go to a separate ground for the cap. Troubleshooting Tips If everything is configurred using the above guidelines and you still have noise, then try to figure out what is causing the noise . First, double check all grounds at amplifiers, crossovers, radio, etc. Make sure the antenna is well grounded. Try to isolate the source of the noise. Bypass crossovers, signal processors, equalizers, etc, by connecting RCA cables straight from the radio to the amplifier. If the noise goes away, this is an indication the problem may be RCA wires or grounds hooked up to crossovers/equalizers. If you have more that one amplifier and have noise only on one amplifier try switching RCA cables around. If noise stays the same, then problem is the amplifier, if it switches, noise is coming from previous components up the line. As said before, it is very hard to find out what is causing alternator noise. Noise filters Noise filter devices should be considered once you have exhausted all the remedies we suggest above. These usually go in the battery + line. Active filtration is better than a passive filter. For a selection of such filters see our page here. The Ans-80 is one of our most effective and popular models. In the next to last resort, you might try an audio line filter. But this has the effect of substantially diminishing frequency response and otherwise changing the nature of the signal. Choose your filter carefully, purchase is at your own risk! If you have tried everything, and still have that annoying noise, contact your nearest car electrial technician.	Sponsors The Electronics Superstore WM Publishing Barbara The Novel Cute The Novel Season's Readings Essays MetroDirect The Amp Depot Powercaps Logos & Banners Bleep Them R. LeBeaux

Home -- Search -- Products -- Tech Help -- Humor -- Links -- Link To Us -- Contact What's New -- What's Hot -- On Sale -- Our Philosophy -- Testimonials © Copyright 2000 - 2009 ElectronixWarehouse - All Rights Reserved - Website Designed And Maintained By MetroDirect Communication
Welcome To The Stereo Technical Information Center. We Offer: Stereo Technical Information Of All Kinds, Including: A Glossary Of Technical Terms, Links To Manufacturer's Websites, Information On How Speakers Work, Choosing Speakers, What's A Woofer?, What's A Midrange?, What's A Tweeter?, What Are Dual-Cone/Dual-Voice-Coil/Full Range Speakers?, 2/3/4-Way & Component Speakers, What's A Capacitor?, Installing A Capacitor, What's A Crossover?, What's An Equalizer?, Speaker Enclosures, Power Amps. Installing An Amp, Amp Installation Tips, Understanding Power Ratings, Installing & Replacing Head Units/Receivers, About Theile/Small Parameters, Installing Neon/LED, Eliminating Unwanted Noise, Using The Right Tools, Home Stereo Tech Information, Frequently Asked Questions, Home Stereo Glossary, About Home Speakers & DriversPlus Sales Of Car, Home and Mobile Audio and Stereo, Marine Audio, Technical Information, Amplifiers, Mono Block Amps, Woofers, Speakers, Mid Range, Tweeters, Capacitors, Woofer Boxes, Bandpass, Bass Reflex Enclosures, Woofer Tubes, Receivers, CD Players, MP3, Satellite Radio, CD Changers, Bass Packages, Car Alarms, Remote Starters, Car Security, Keyless Entry, Wiring and Accessories, Antenna Boosters, Antennas, Bass Blockers, Crossovers, Dynamat, Equalizers, Cooling Fans, Noise Filters, Power Inverters, Power Supplies, RCA Cables Splitters, Remotes, Signal Boosters, Speaker Grills, Vibration Control, Wiring, Mobile Video, Personal and Mobile Electronics, Laptops, Cell Phones, PDAs, GPS, Electronic Books/Readers, Kindle, MP3, Earphones/Buds, Blu-Ray, Bluetooth, Calculators, Marine Stereo, Fish Finders, Flat Screen HD TVs, DVD Players, Tivo, DVD Recorders, Surround Sound, Stereo Drivers, Home Speakers, Enclosed Subwoofers, Video Games, Computer Games, Digital Photo Frames, Computers, PCs, Laptops, Monitors, Software, Printers, Scanners, Computer Supplies, Virus Security.