Left ear no music

Have you use another headphones insteading of your Sony headphones to have a try? Make sure it is not the problem of headphone, then you may need a headphone jack replacement to replace the old one.
I've also met this situation with my phone. Finally I found the right
Headphone Earphone Audio Jack Flex Cable for Samsung Galaxy S4 i9500 to solve this problem. You can also look for one repair part for your phone, then find a video following to fix. It is easy to make it. Hope it can help.

Nope - headphones do nothing to protect ears from loud noise. Actually they can make it worse as listening to loud music directly in the ears can be quite dangerous.

sounds like you have removed them by pulling on the wires, not by the earbuds or plug. not a recommeded practice when unplugging anything as it usually ends in broken wires internally along with tears. You may be able the get somebody to do some faultfinding/repairs if they are of the super expensive variety otherwise replacement may be the only solution. Most in-ear headphones have super delicate wiring and are as such a real pig to resolder

Right now I am having the same problem. When the bass goes high it's an awful noise like rattling and I'm afraid I blew the speakers. But I was only listening to them on a simple iPod 3rd gen. Please helpppp!!!!

sounds like a broken wire. have them exchanged.

I had the same problem with a Samsung phone. There are two ways of fixing this; First, you can remove the S9 profile from your phone's bluetooth list, and then add it again, going through pairing and entering 0000 on your phone when asked for the code.
Alternatively, you might try pressing the "play" button on the right earpiece on the Motorola S9. This is supposed to kick it into the A2DP stereo mode for music listening.
Good luck.
And get a copy of the manual from the Motorola web site at http://direct.motorola.com/ens/s9/Headset_Home.asp I found this very handy for checking what the little flashing lights mean. When you get stereo reception, the little LED in the middle of the headset flashes green, not the usual blue and red and purple for voice calls. 
In case you didn't know, as a phone headset, with the microphone activated, you only get sound in your left ear, and the light flashes blue. For music, you get both ears, and it flashes green. So if it ain't green, you are in mono mode.

This is either cause by a damaged headphone socket in the iPod or a loose connection. The only way to solve it will involve opening the iPod case and inspecting the daughter board that the headphone socket is on.

headphone jack needs to be resoldered.

The headphone jack on all the apple products have issues (even their laptops). There is no easy fix, other than having the jack replaced, or remounted. A common issue is that it comes loose from the pc board, especially with the movement of the headphone cord. This is a design/functionality flaw.

Hope this helps some.

TWEAK A/V LAB

I recently purchased a Sansa e280 and in three weeks of regular use it developed a similar problem, with music cutting out from playing in stereo to mono, coming out of one headphone speaker. Sandisk tech support told me to reformat the device and install the latest firmware, which I did, but the problem continued and occured more frequently. I have returned the player back to the seller and I shall not be getting another one. A nice Ipod alternative from Sandisk, but from what I have seen written about in forums, the Sansa e200 series appears to be buggey with problems.