WhatsApp voice message is used by most people who dislike typing and wanted to convey message faster. However, the current version of WhatsApp requires user to stay on the screen while listening to voice message. Now, WhatsApp is testing a new feature that allow them to listen to voice message even when the app is exited to background, according to WABetaInfo.
User are allowed to play or stop the recording through the blue bar. This feature will be roll out when its available.