Boost Volume of Inaudible Audio Recordings for Free

Audacity is a free and open source soft ware which is used for audio recording and editi ng. The cross-platf orm soft ware can be downloaded from htt p://ld2.in/4he. Among the many uses at which it can be put to task, one is to arti fi cially increase the amplitude of the sound signal that gets encoded in the audio fi les, thereby eff ecti vely increasing the perceived volume of the sound to the listener.

Of course, this won't act as a workaround in case the sound itself has been recorded in an undecipherable manner. But in case all that is needed by the listener is to make out words from what feels like mere whispers, a volume boost can help and this is possible at any ti me post the recording irrespecti ve of whether you acti vated `Mic boost' or not at the ti me of recording. Audacity for Windows is available both in the form of an installable setup as well as in the form of a ZIP fi le (which is smaller because it doesn't contain help fi les).

How to use it

Audacity supports a host of diff erent formats including WAV, OGG, MP3, AIFF, etc. Here we try to read a prerecorded stereo WAV fi le on a Windows XP system and try to boost the volume of a part.

1. When you try to open the audio fi le from the `File' menu, aft er selecti ng the fi le, you will be presented with two choices. You can either make a copy of the said fi le and then edit it, which is obviously safer or you can read the fi le directly from the original, which will be fast. We chose to read the fi le directly.

2. Opening the fi le will result in displaying the sound signals on a ti me frame, much like the snickometer displays used to detect contact of the ball with the bat in a cricket match. You will be immediately able to make out just by having a glance as to which part of the recording is of low volume and where the volume is high enough.

3. To accurately determine the porti on of the audio that needs a volume boost, play through the fi le (by selecti ng the Play opti on from the Transport menu) and make a note of the ti mestamps of the porti on concerned. Then, either by using the mouse or by using the required `Select' opti ons from the `Edit' menu, highlight the region.

4. Aft er ensuring that the correct porti on has been highlighted, select `Amplify' from the `Eff ects' menu and then choose the amplifi cati on (in dB) required. Aft er selecti ng an amplifi cati on level of 20 and selecti ng to allow clipping, we got the end result as follows. Note the change in the volume of the selected region compared to the unselected region. At this point, you may want to try playing the fi le again to ensure that the level is now just right to be heard. If not, use the `Undo' opti on from the `Edit' menu.

5. To save the file, select `Export' from the `File' menu and keep the file name and file type as it is to ensure replacement of the original. After confirming the replacement and editing any metadata, close the file. It's not necessary to save the changes made since we have already exported the file. Exit Audacity. You will also find that the original file has been saved with an appendix of `-old1` to it's file name in the same folder.