Some Intervoice customers have reported clicks and pops in messages that have been created in Sound Forge for use on Intervoice's IVR platform. Sometimes the clicks are at the end of messages, between concatenated messages, or in the middle of the message. There are several types of clicks that can occur, and each type has a different cause and solution. To help identify the causes of clicks in messages, they can be split into two categories:
- Category 1: Clicks that can be heard when the message is played during the Sound Forge edit process.
Generally, these clicks in a message are caused by problems during the audio recording process. Mouse clicks, a table tap, breath pops, or computer keystrokes are typical causes of these clicks. Rarely, on some slower PCs, Sound Forge itself will cause a click when starting or ending a message; this is caused by buffer under/overruns.
Re-recording the message is the best way to eliminate these types of sounds. However, if re-recording is not an option, Sound Forge has many tools that can help you eliminate these clicks. The Mute Segment preset, Delete Segment function, or Pencil Tool features can be used to edit the click out of the audio. For breath pops, the Multiband Dynamics "Reduce Loud Plosives" preset is effective.
- Category 2: Clicks that cannot be heard during the Sound Forge edit process, but can be heard on the Intervoice runtime system over the phone.
These clicks tend to be more difficult to diagnose, since they are not audible in Sound Forge. These types are typically caused either by the compression process or the playback mechanisms on the Intervoice platform. These types of clicks can occur at the beginning or end of a message, between concatenated messages, or in the middle of a message. The position of the click helps determine the possible cause.
Clicks of this type in the middle of a message are typically caused by background noise and DC offset in the original message. Intervoice stores messages using a standard G.721 32 Kbps ADPCM compression algorithm to reduce the size of message storage. The G.721 compression process is fairly sensitive to both DC offset and background noise, so both of these should be minimized in the recording process before the final compression step is performed.
- Noise Floor
Always check the background noise and noise floor of your recording studio and equipment before starting a recording session (see Sound Forge noise floor test). - Automatic Gain Control (AGC) on sound cards
Be sure the AGC is disabled on the Creative Labs Sound Blaster card (see Frequently Asked Questions (FAQs)). - DC Offset
Be sure that the DC offset is removed from messages (see Frequently Asked Questions (FAQs)).
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