Some songs automatically lowering volume when syncing?

Hi so I downloaded a few albums that are all labeled as 320kbps. When I play them on my computer, they all sound perfect. However, when I sync them to my iPhone, it seems that some of the albums decided to lower the volume of its songs automatically... This is really annoying because when I have the volume set to say... 10, it sounds great for album A, but album B sounds like its on volume level 5...

Why is this happening on my phone but not my computer? How can I fix this??

Thanks in advance.

songs/albums are recorded at different levels (of loudness, measured in DB) There is a fix that is available and standard but apple hasn't implemented it. It's called Replay Gain, apple has made their own "competitor" to it, but it's nowhere near as good. email apple to add replay gain (i already did, i have a 4s), it is a standard now in the industry, apple's just behind (not a surprise). Other option is rockboxing an ipod classic for music. (mod, there's a thread on head-fi)

also what headphones do you use? that could be the reason why it might sound so low in terms of volume.

another option you have is buying a portable headphone amp to go along with your iproduct so you can control inccrease/decrease loudness. (really not necessary, unless you're using higher headphones that need an amp to drive). There's alot of portable headphone amps under $100 that'll work.

Ahhhh. I figured it out. It turns out that I had set SoundCheck to "On" probably a while back because maybe I thought that it would solve the problem but it turns out that for some reason it was the cause of the problem... Now my songs are all playing equally as loud.

Thanks anyways!