Why does the app produce an unexpected sound on a real device but work correctly on the iOS 26.5 simulator?

Question

Hi Friends,

I am currently working on the app store applications that are designed to support vehicle maintenance and repair by pairing smart hardware sensors with real-time digital graphing, noise analysis, and data logging. By providing accurate visual data, these applications help replace traditional mechanical guesswork with precise and reliable information for vehicle diagnostics and repair.

As part of the current update, around seven applications have been added to the test list. During the testing process, I found that three applications are experiencing some issues that require further investigation.

Problem Identified

The MTS 1 and SS1 applications have been updated and tested using iOS 26.5 on the simulator with Xcode 26.6. Both applications are working correctly in the simulator, and I have not observed any issues during the simulator testing.

However, when the applications are installed and tested on a real physical device, they do not work as expected. The main issue is that the applications produce an unexpected or abnormal sound during operation. This sound does not occur when running the applications in the simulator.

Therefore, there is a difference in behavior between the simulator environment and the real device. Further investigation is required to identify the root cause of this issue and determine whether it is related to the iOS version, device configuration, hardware interaction, audio processing, or any other device-specific behavior.

Please feel free to share your thoughts, suggestions, or any ideas that might help identify the cause of this issue.

Thank you!

Answer 1

Big question is how do you test this in simulator? How do you get input sound to simulator?

Comments

When running the Xcode Simulator, the application defaults to using the Mac's microphone as its audio input source.

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Did you tried using earphone in mobile device? May be issue is with test hardware?

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yes, i tried.

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I tested it with a Bluetooth-connected earphone.

Answer 2

Since the applications are working correctly on the iOS 26.5 Simulator but producing an unexpected sound on the physical device, I would suggest first checking whether the issue is related to the physical device or the connected hardware rather than the simulator/iOS version alone.

In particular, it may be worth checking:

• AVAudioSession configuration and audio output routing.

• Whether the application is accessing the microphone or audio input/output differently on a real device.

• Bluetooth communication and the connected smart hardware/sensor.

• Whether the sound is generated by the phone speaker, Bluetooth device, or the hardware itself.

• Any audio processing or sensor SDK that behaves differently on a physical device.

• Device logs/Console logs while reproducing the issue on the real device.

It would also be useful to test the same build on another physical iPhone/iPad and, if possible, with the hardware/Bluetooth connection disconnected. This can help isolate whether the issue is device-specific, hardware-related, or caused by the application.

Since the simulator does not fully replicate physical hardware and Bluetooth/audio behavior, comparing these different scenarios should help narrow down the root cause.

Answer 3

have you checked whether similar sounds are present in the existing build of the application?

Answer 4

One possible reason could be that the issue is related to the difference between the iOS Simulator and the physical device, especially since the sound occurs only on the real device.

I would suggest checking the following:

1. Audio Session configuration – Verify AVAudioSession settings such as category, mode, and activation. An incorrect audio session configuration can sometimes produce unexpected audio behaviour on a physical device.

2. Hardware/Bluetooth interaction – Since these applications communicate with external vehicle sensors/hardware, check whether the unexpected sound is related to Bluetooth or the connected hardware. Testing with the hardware disconnected could help isolate this.

3. Audio output route – Check the actual audio route on the physical device using AVAudioSession and confirm whether the sound is being routed through the expected output.

4. Compare device logs – Capture the Xcode console/device logs while reproducing the issue on the physical device and compare them with the simulator logs. Any audio-session, Bluetooth, or Core Audio warnings may help identify the cause.

5. Test on another physical device – If possible, test the same build on another iPhone. This can help determine whether the issue is device-specific or related to the application itself.

6. Test with different iOS versions – If the issue occurs only on a particular iOS version, it may indicate an iOS/device-specific compatibility issue.

Since the application works correctly on the simulator but produces the sound on a physical device, I would first focus on AVAudioSession configuration, audio routing, and the connected hardware/Bluetooth communication.

These checks may help narrow down the root cause before making code changes.