/usr/include/portaudiocpp/ is in portaudio19-dev 19.6.0-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/portaudiocpp/AutoSystem.hxx
/usr/include/portaudiocpp/BlockingStream.hxx
/usr/include/portaudiocpp/CFunCallbackStream.hxx
/usr/include/portaudiocpp/CallbackInterface.hxx
/usr/include/portaudiocpp/CallbackStream.hxx
/usr/include/portaudiocpp/CppFunCallbackStream.hxx
/usr/include/portaudiocpp/Device.hxx
/usr/include/portaudiocpp/DirectionSpecificStreamParameters.hxx
/usr/include/portaudiocpp/Exception.hxx
/usr/include/portaudiocpp/HostApi.hxx
/usr/include/portaudiocpp/InterfaceCallbackStream.hxx
/usr/include/portaudiocpp/MemFunCallbackStream.hxx
/usr/include/portaudiocpp/PortAudioCpp.hxx
/usr/include/portaudiocpp/SampleDataFormat.hxx
/usr/include/portaudiocpp/Stream.hxx
/usr/include/portaudiocpp/StreamParameters.hxx
/usr/include/portaudiocpp/System.hxx
/usr/include/portaudiocpp/SystemDeviceIterator.hxx
/usr/include/portaudiocpp/SystemHostApiIterator.hxx