AVAudioSession 的 PlayAndRecord 类别和 AVAudioSessionModeMeasurement 与 defaultToSpeaker 选项不兼容？
AVAudioSession's PlayAndRecord category and AVAudioSessionModeMeasurement are incompatible with defaultToSpeaker option?
尝试将 AVAudioSession 放入带有 AVAudioSessionModeMeasurement 模式的 .playAndRecord 类别会导致 .defaultToSpeaker 选项被忽略，导致输出在耳机中安静地播放（也称为接收器）。
虽然关于此的内容似乎不多，但文档使此 "end result of audio output being sent to the receiver rather than speaker" 看起来像是可能的预期行为，而不是错误。
let AVAudioSessionModeMeasurement: String
This mode is intended for apps that need to minimize the amount of
system-supplied signal processing to input and output signals. If
recording on devices with more than one built-in microphone, the
primary microphone is used.
尝试将 AVAudioSession 放入带有 AVAudioSessionModeMeasurement 模式的 .playAndRecord 类别会导致 .defaultToSpeaker 选项被忽略，导致输出在耳机中安静地播放（也称为接收器）。
虽然关于此的内容似乎不多，但文档使此 "end result of audio output being sent to the receiver rather than speaker" 看起来像是可能的预期行为，而不是错误。
let AVAudioSessionModeMeasurement: String
This mode is intended for apps that need to minimize the amount of system-supplied signal processing to input and output signals. If recording on devices with more than one built-in microphone, the primary microphone is used.