Degraded or crackly audio during voice calls is highly likely to be an indication of poor internet connectivity. Below is a list of steps that you can take that will help determine the reason for your reduced call quality, and the steps that can be taken to assist in recovering the quality.
Determining the cause
The first step to take is to determine how your internet speeds are compared to the speeds that you are meant to have. To find your current speed you can use a speed test website such as this one. Once you have the test results, you can see if the impact is due to a slow internet connection.
Correcting the cause
If you find that there is a poor internet connection, the next step is to find the cause and resolve it.
Close your apps
A common issue would be if you are using Microsoft OneDrive, DropBox, SharePoint, Google Drive, etc. As these can use a large amount of data at a time. Closing applications like this that use large amounts of data may yield an increase in the audio quality.
Speak to your IT team
Speak to your IT team about the degraded voice quality as your router may need to be configured for Quality of Service. Quality of Service (QoS) is a feature of modern business-grade routers that prioritise voice-based network traffic. This router setting will assist in ensuring that there is enough data reserved for VoIP phone traffic.