有個方法..不知好不好用..你參考看看囉
你可以安裝 sonicfoundry Sound Forge 6.0 以後版本
直接開啟這個 mpeg1 檔
然後用 SoundForge 的聲音調整功能..將聲音放大
然後再存檔 (不過這樣等於重新壓縮檔案..可能要花一些轉檔時間喔)
調整後的聲音不錯啦..因為..我也曾試過 ^.^

1.TMPEGEnc開啟該檔後,右側的Stream Type選擇Audio Only,
2.按下面的Setting進入Audio視窗,
3.下面的Use Audio Edit的Setting就有一個Change Volume,
　預設是100,把它往上調整到你滿意的音量,即可存成mp2.

建議採用premiere6.5或sonic公司出有關聲音處理產品,應該有不錯的效果, (但請注意, 所有這類的軟件並不建議將volumn過份提升, 否則會弄致出現嚴重雜音,及變質, 因此仍建議改善擷取時的質素.


另外, 有部份網頁不建議採用tmpgenc單獨處理聲音檔......

摘自tmpgenc setting網頁
There are two reasons not to encode the audio in TMPGEnc:

The first is the fact that MPEG audio is not standard on all DVD players. Although it is supported by all PAL players (and many recent NTSC models), some authoring programs still refuse to add MPEG audio directly to their projects, and will instead convert it to PCM (uncompressed). Since MPEG audio uses lossy compression, the quality that was lost in the compression is not recovered. By contrast, the space that was saved by the compression is lost again. So, using MPEG audio in these programs is a lose-lose situation. The only two formats guaranteed to be compatible with all players are PCM and AC3.



The second reason is the fact that there are several MPEG audio encoders that produce better quality than TMPGEnc. So even if your authoring program does support MPEG audio, and if you're sure the resulting discs will only be played on DVD players that support MPEG audio, you should still use TMPGenc only for the video, and encode the audio in a separate application (if you do a quick search on the web for "MPEG audio encoding" you should be able to find several guides about the subject).

這套軟體好貴ㄝ,我實在是玩不起
看來我還是乖乖的用tmpgenc就好
不過還是謝謝大家幫我回答

起碼我已經有方法可以解決問題了^^