When finding yourself in a noisy environment, it's difficult to listen to voice messages that are sent to you. The same is true when sitting in class, for example. Voicer for WhatsApp turns voice messages into written text at the push of a button. Simply highlight the voice message in your messaging client by long-pressing on it, tap the "Share"-button, and select "Voicer for WhatsApp" from the list of possible sharing targets. The voice message will then appear as written text!
You can use the app's settings menu to change the recognition language. The app supports 50+ languages.
I have to pay a fee to Google for each transcribed message, so I had to introduce a payment system. You get two free credits to try the app, afterwards you'll have to purchase a credits-package to continue using the app.