Issue is also present on 4.6.4. Appear to be only on iOS 7, but not 6 or 8.

We are using Unity 4.3.4 for iOS7 and when the app gets interrupted by Siri or alarm clock, audio goes silent.

Hello Unity support,

We are working on Unity 4.2.2 and Unity 4.3.1 and we are getting an issue when using the WebCamTexture on iOS 7, the issue happens when the application is using the WebCamTexture and a system interrupt popup appears (for example an alarm interrupt, a timer interrupt or a phone call interrupt) the audio of the application stops working. The only way to get the audio working again is closing the app and running it again.

The following post was found on the issue tracker (http://issuetracker.unity3d.com/issues/ios-audio-wont-play-after-receiving-call), it is the same issue that we are getting, but there are no answers yet.
This simple test code was created to reproduce this issue:

using UnityEngine;
using System.Collections;

public class WebCamTest : MonoBehaviour
{
[SerializeField]private AudioClip clip;

void Start()
{
GUITexture guiTexture = gameObject.AddComponent<GUITexture>();
guiTexture.pixelInset = new Rect(0, 0, Screen.width, Screen.height);

WebCamTexture webCamTexture = new WebCamTexture();
guiTexture.texture = webCamTexture;
webCamTexture.Play();
}

void OnGUI()
{
if(GUI.Button(new Rect(10, 70, 300, 150), "Click"))
audio.PlayOneShot(clip);
}
}

Steps to reproduce:

1- Create an empty project with an empty scene, create an empty game object and assign a script with the test code, assign any audio on “AudioClip clip” variable.
2- Generate the Xcode project for iOS.
3- Run the test app on a device with iOS 7.
4- Use the GUI button to reproduce the sound, notice, the WebCamTexture is rendering the camera input on screen and the audio is playing correctly.
5- Open iOS clock application and start the timer for a minute.
6- Open the test app again use the button to reproduce the sound, notice, it is still working.
7- Once the timer interrupt appears close the interrupt popup. (An alternative way for this step is receiving a phone call interrupt dialog).
8- Use the GUI button to reproduce the sound, notice, the sound stop working, any sound played on Unity won’t play again.

Could you help us to fix this issue?

Thank you in advance for your help.

The same issue happens to me using Unity 4.2.2 and Unity 4.3.1 for iOS 7. I make a test project with one single camera using WebCamTexture and after receive a clock alarm, when I try to play an audio again, the audio not working anymore.