import QtQuick 2.12
import QtQuick.Window 2.12
import QtMultimedia 5.8

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    Audio {
        id: audio
        loops: Audio.Infinite
        onStatusChanged:        console.log("status = " + status)
        onError:                console.log("error = " + error + " " + errorString)
        onPlaybackStateChanged: console.log("playbackstate = " + playbackState)
        source: "qrc:/sounds/audio.mp3"
        volume: 1.0
    }
    Component.onCompleted: audio.play()
}

I have a sounds subdirectory at the same level as my .pro file and I have added sounds/audio.mp3 to the qrc. This works fine on eg Linux and Mac. When running this application on an actual iPhone, I see the following loglines

QML debugging is enabled. Only use this in a safe environment.
qml: status = 2
stale focus object QObject(0x0) , doing manual update
qml: playbackstate = 1
qml: status = 6
qml: status = 7
qml: status = 3
qml: playbackstate = 0
qml: status = 6
qml: playbackstate = 1
qml: status = 7
...

so it seems that the file is found and played back correctly. However, I can hear nothing at all. Other apps on my Phone do play sounds.

I've also tried using a construct like in my *.pro file as suggested here

SOUND_FILES = ./sounds/audio.mp3
ios {
  sound.files = $$SOUND_FILES
  sound.path = sounds
  QMAKE_BUNDLE_DATA = sound
}

but by doing so, I always got qml: error = 1 Attempting to play invalid Qt resource (I tried /sounds/audio.mp3, sounds/audio.mp3, audio.mp3)

Any ideas? A working example maybe?