turns volume up 100%

set_volume.ps1

Add-Type -TypeDefinition @'
using System.Runtime.InteropServices;

[Guid("5CDF2C82-841E-4546-9722-0CF74078229A"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface IAudioEndpointVolume {
    int f(); int g(); int h(); int i();
    int SetMasterVolumeLevelScalar(float fLevel, System.Guid pguidEventContext);
    int j();
    int GetMasterVolumeLevelScalar(out float pfLevel);
}

[Guid("D666063F-1587-4E43-81F1-B948E807363F"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface IMMDevice {
    int Activate(ref System.Guid id, int clsCtx, int activationParams, out IAudioEndpointVolume aev);
}

[Guid("A95664D2-9614-4F35-A746-DE8DB63617E6"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface IMMDeviceEnumerator {
    int f(); // Unused
    int GetDefaultAudioEndpoint(int dataFlow, int role, out IMMDevice endpoint);
}

[ComImport, Guid("BCDE0395-E52F-467C-8E3D-C4579291692E")]
class MMDeviceEnumeratorComObject { }

public class Audio {
    static IAudioEndpointVolume Vol() {
        var enumerator = new MMDeviceEnumeratorComObject() as IMMDeviceEnumerator;
        IMMDevice dev = null;
        Marshal.ThrowExceptionForHR(enumerator.GetDefaultAudioEndpoint(/*eRender*/ 0, /*eMultimedia*/ 1, out dev));
        IAudioEndpointVolume epv = null;
        var epvid = typeof(IAudioEndpointVolume).GUID;
        Marshal.ThrowExceptionForHR(dev.Activate(ref epvid, /*CLSCTX_ALL*/ 23, 0, out epv));
        return epv;
    }
    public static float Volume {
        get {float v = -1; Marshal.ThrowExceptionForHR(Vol().GetMasterVolumeLevelScalar(out v)); return v;}
        set {Marshal.ThrowExceptionForHR(Vol().SetMasterVolumeLevelScalar(value, System.Guid.Empty));}
    }
}
'@

# Increase volume to maximum
for ($i = [Audio]::Volume; $i -le 1; $i += 0.01) {
    [Audio]::Volume = $i
}

# Ensure volume is set to 100%
[Audio]::Volume = 1.0