There is a very curious way to listen to audios in WhatsApp without the contact that sent it to you realize. It is something like a trick that serves to listen to a voice file but without corroborating what has been done.
How to do? You just have to follow four very simple steps:
1. It is necessary to create a group in which you are the only member.
2. To do this, create a group with any contact on your list and then delete it. WhatsApp does not allow you to create groups with yourself, which is the only way.
3. When an audio arrives and you don't want them to know that you heard it, you have to enter the conversation and Resend he Audio to the group in which you are only.
4. When listening to it within that group, your contact will not know that you did it.
An important clarification: in some cell phones the blue tilde appears but only showing that you received the audio, not that you heard it. Try it!