A rattle or buzz coming from the TV that coincides with the audio can either be an acoustic problem or an electronics problem.
If the noise occurs with either certain tones in the audio or along with a majority of the soundtrack, the probable cause could be one of these:
- External resonance - vibration of an object near the TV
- Internal resonance - vibration of something inside the TV
- The speakers themselves, or
- A faulty main (signal) board
If the TV is located inside of a large cabinet or an entertainment center, listen carefully to see if the noise is coming from something around the cabinet such as a vase, curio, or picture frame. Try removing anything of this nature from the vicinity of the TV and see if the noise goes away.
If you suspect that the noise is coming from inside the TV's own cabinet and the TV is still under warranty, have a service technician come out and fix it. If the TV is out of warranty, there are things you can do to fix the problem yourself. You will need to get some friction tape and some electrical tape. And you will have to remove the back cover of the TV. See How Do I Get To the Circuit Boards in a TV? to learn how to remove the back cover.
With the back cover removed, apply friction tape along the lip of the bezel (frame) where it meets the back cover, and anywhere else that might cause the back cover to rattle against the panel superstructure. Then, secure any loose wires or cable bundles that are dressed along the inside of the cabinet by taping them against the cabinet with electrical tape.
You can tell if a speaker is blown if the sound coming from it is fuzzy at any volume level, or if it makes loud popping noises at high volumes.
Speakers are commonly replaced in flat screen TVs because they are so easily blown. They can be damaged by excessively loud, “boomy” music. The good news is they are not very expensive.
To avoid blowing the speakers in your TV, keep the bass and treble controls near mid position, and don’t crank-up the volume beyond the level of a normal conversation.
One way of testing speakers is by using a test signal. Go to www.myTvTestPatterns.com, and download the Audio Vibration Sweep test pattern, one of many video test signals available on this web site. This test signal produces an audio tone that sweeps across a low-frequency range. The tone can be used to check for acoustic vibration.
Play the vibration test signal with the volume set to a low setting and then listen for a buzz in the speakers. If the buzz only occurs at particular places along the sweep (resonant frequencies), the problem is most likely something other than the speakers, as previously discussed. If the buzz is heard across a wide portion of the sweep, then the speakers are bad. If the buzz is heard over the entire sweep, or if it sounds like there is a scratchy distortion or a rushing noise mixed with the tone, then the problem is electronic and the main board would need to be replaced.
Why Is The Sound Quality from the TV So Poor?
In order for TV manufacturers to make their TVs as flat as possible, they have to make compromises in their designs. One of the biggest tradeoffs involves the speakers. The early flat screen TVs contained thin, flat, oval speakers facing the front. Many of today’s flat screen TVs have speakers located at the bottom of the cabinet facing down. The speakers are 1½-by-½ inches (3.5-by-3.5 cm), mounted in skinny 5-inch (13-cm) long plastic enclosures. In the more recent ultra-thin LED TVs you will find 1-by-½ inch (3-by-7 cm) speakers mounted in 6-inch (15-cm) square enclosures that are about as thick as a pancake. These speakers project the sound toward the back of the TV. Needless to say the sound quality that comes from these kinds of speakers is no match to what a larger speaker system can provide. This is why many people choose to connect a sound bar speaker system, or an A-V receiver and sound system to their TV.
If the noise is constant and seems to have no coorelation with the audio, then the cause is most likely electronic. Here is how you can find out if the problem is the TV:
- Try listening to more than one source, i.e. a DVD, video game, or off-air TV. If you hear the problem from only one device, then the cause is probably that device. As a workaround, try connecting whatever that device is to the TV another way (via HDMI, component video, or composite video are three possible ways) and see if the problem goes away.
- Try other audio output devices. Most TVs have either optical or analog audio output jacks. If it is possible to connect one of these outputs to another device such as an A-V receiver, see if you can still hear the problem that way.
- If the TV is connected to an A-V receiver, disconnect or mute it and turn-up or enable the volume on your TV speakers. If you don't hear the problem that way, then your A-V receiver or speakers are at fault.
- If the problem occurs with every input device or signal source, then all fingers point to the TV.
If you have determined that the problem is in the TV, then you will need to replace the main (or signal) circuit board. Go to Replacing Circuit Boards and How to Order TV Parts for details about how to do this.
If the problem is that there is an echo in the sound, perform a software update on the TV.