WhatsApp, the popular instant messaging service, has turned on a voice messaging feature across all the mobile platforms it supports, including Windows Phone. The new feature, which does not require an app update, allows you to send and receive audio messages, providing an alternative to the existing text, picture, and location messages.

WhatsApp says it has spent a lot of time making it as easy as possible to send and listen to voice messages, and clearly feels that it has done a better job in implementing voice-based messages than rivals services who already have the feature.

On Windows Phone new voice messages can be recorded by pressing and holding the microphone icon next to the standard text entry box (when viewing a conversation), with the voice message being sent automatically when you lift your finger off the microphone icon. Received messages are shown with an in-line media player, letting you listen to them by tapping the on screen play button.

On Windows Phone 8 devices WhatsApp uses the phone's sensors to work out what loudspeaker to play the message through. If you hold your phone up to your ear (activating the proximity sensor) the audio will play through the ear piece, otherwise audio will play through the main loudspeaker. This makes it easier to listen to private messages, without a risk of being overheard.

Message status is indicated by a coloured icon, with a green icon indicating a voice message you have not listened to, and a blue icon indicating a voice message that you have listened to. The same system applies to sent voice messages, allowing you to see, at a glance, whether the person you are communicating with has listened to the voice message you sent.

The new feature is currently rolling out. It should be available to all users in the next 24 hours.

Here's a video from WhatsApp that shows the voice messaging functionality in action:

WhatsApp's latest numbers indicate that it has more than 300 million monthly active users, and that more than 11 billion messages and 325 million photos are sent through the service every day. That makes it the biggest mobile first instant messaging service by some distance.

Windows Phone Store description:

WhatsApp Messenger is a smartphone messenger available for Windows Phone, Android, BlackBerry, iPhone, and Nokia phones. WhatsApp uses your 3G or WiFi (when available) to message with friends and family. Switch from SMS to WhatsApp to send and receive messages, pictures, audio notes, and video messages. 

WhatsApp is a free download from the Windows Phone Store. It is free to use for the first year, after which a $0.99 annual subscription is required.