How to detect Proximity Sensor?

Question

how to detect whether the user hear this audio in proximity or not?

Answer 1

First detect state of Proximity Sensor using iPhone Proximity Sensor and then play audio using phone call speaker Play audio through upper (phone call) speaker

Answer 2

[[UIDevice currentDevice] setProximityMonitoringEnabled:YES]
[[NSNotificationCenter defaultCenter] addObserver:self
    selector:@selector(sensorStateChange:)
    name:@"UIDeviceProximityStateDidChangeNotification" object:nil];