iOS AVAudioSessionCategory unexpected behaviour

I'm having an issue trying to use the

AVAudioSessionCategorySoloAmbient

My intent is to play a sound when my ViewController first opens. But only if the ringer is on

However, the sound plays regardless of whether the ringer is on or off.

I don't have access to a device so I'm only testing on the simulator.

This is a completely fresh project, everything being what XCode automatically generates, with only the following file altered

The ViewController is as follows

import UIKit
import AVFoundation
        
class ViewController: UIViewController {
        
     var audioPlayer: AVAudioPlayer?
            
     override func viewDidLoad() {
          super.viewDidLoad()
          do {
               try self.playSound(file: "startup", ext: "wav")
          } catch {
               print("Something went wrong")
          }
      }
            
      func playSound(file: String, ext: String) throws {
           let path = Bundle.main.path(forResource: file, ofType: ext)!
           let url = URL(fileURLWithPath: path)
        
           let session = AVAudioSession.sharedInstance()
           try session.setCategory(AVAudioSessionCategorySoloAmbient)
           try session.setActive(true)
                
           self.audioPlayer = try AVAudioPlayer(contentsOf: url)
           self.audioPlayer?.prepareToPlay()
           self.audioPlayer?.play()
      }
}

 

As I understand it, what I want should be the default behaviour anyway. So I have also tried omitting the following lines. But the same thing happens.

           let session = AVAudioSession.sharedInstance()
           try session.setCategory(AVAudioSessionCategorySoloAmbient)
           try session.setActive(true)

I'm using Swift 4.1

Any help appreciated!