diff --git a/share/man/man4/snd_uaudio.4 b/share/man/man4/snd_uaudio.4
--- a/share/man/man4/snd_uaudio.4
+++ b/share/man/man4/snd_uaudio.4
@@ -60,9 +60,54 @@
 Refer to the
 .Ql USB Audio Class Specification
 for more information.
+.Sh SYSCTL VARIABLES
+The following variables are available as both
+.Xr sysctl 8
+variables and
+.Xr loader 8
+tunables.
+For a change to take effect during runtime, the device has to be re-attached.
+.Bl -tag -width indent
+.It Va hw.usb.uaudio.buffer_ms
+Buffering delay in milliseconds, from 1 to 8 (default is 4).
+.It Va hw.usb.uaudio.default_bits
+Default sample bits, from 0 to 32 (default is 32).
+A value of 0 sets the sample bits to the maximum supported value.
+.It Va hw.usb.uaudio.default_channels
+Default sample channels, from 0 to 64 (default is 0).
+USB 1.1 devices are limited to 4 channels due to bandwidth constraints.
+A value of 0 sets the sample channels to the maximum supported value.
+.It Va hw.usb.uaudio.default_rate
+Default sample rate.
+If set to 0, the device's defaults will be used.
+.It Va hw.usb.uaudio.handle_hid
+Let
+.Nm
+handle HID volume keys, if any (default is 1).
+.Bl -tag -width 2n
+.It 0
+Disabled.
+.It 1
+Enabled.
+.El
+.El
+.Pp
+If
+.Xr usb 4
+has been compiled with
+.Va USB_DEBUG
+on, the following
+.Xr sysctl 8
+variable is also available:
+.Bl -tag -width indent
+.It Va hw.usb.uaudio.debug
+Debug output level (default is 0).
+.El
 .Sh SEE ALSO
 .Xr sound 4 ,
-.Xr usb 4
+.Xr usb 4 ,
+.Xr loader 8 ,
+.Xr sysctl 8
 .Rs
 .%T "USB Audio Class Specifications"
 .%U http://www.usb.org/developers/docs/devclass_docs/