Your screenshot looks like a part of the Gmail app. There's a small arrow at the bottom right of this picture. If you tap it, you get the possibility to open the file in Safari. Try this option.
If this doesn't work, set up the Gmail account on your iPad in Settings - Mails, Contacts, Calendars. Afaik the built in Mail app plays these files without problems. So does the Mailbox app. So if you don't want to use Mail, look for Mailbox in App Store, install it and set it up using your Gmail account.
Hope that helps.
I am told that there is an app that will play wav files. https://itunes.apple.com/gb/app/oplayerhd-lite-best-free-video/id385896088?mt=8
One downloaded, if the wav file is in an email, press and hold the file until an open in box appears and chose the above app to pay it.
This is the normal way of playing email attachments, so I should think it will work.
Sent from my iPad 2 using iPF
That's great!Thanks for all the answers and your time. In the iPad e-mail I have configured my Hotmail account. Opening the wav file in Safari I get the same crossed play icon. If I forward the GMail e-mail with the wav file to my Hotmail account, I can open and play the wav file from there.