Sound not working in Push Native

Ionic Framework ionic-v3
1

Hello,

I am using Push Native. I am receiving notifications but sound is not working. Please help.

Using this code:

let push = Push.init({
            android: {
                senderID: "<sender_id>"
            },
            ios: {
                alert: "true",
                badge: false,
                sound: "true"
            },
            windows: {}
        });