Video decrease the volume

Can someone help me?
I use screenlyOSE in conjunction with a hospital care queue management system. I need the video volume to be lower than the system beep. was changing the file by assigning volume omxplayer command.

def view_video(uri, duration):
logging.debug('Displaying video %s for %s ', uri, duration)

if arch in ('armv6l', 'armv7l'):
    player_args = ['omxplayer', uri, '--vol -600']
    player_kwargs = {'o': settings['audio_output'], '_bg': True, '_ok_code': [0, 124, 143]}
    player_args = ['mplayer', uri, '-nosound']
    player_kwargs = {'_bg': True, '_ok_code': [0, 124]}

I’ve tried it in many ways but unfortunately it didn’t work.
Thank you very much in advance.

I was able to set the volume, I was missing the parameter.
It follows the correct way:
if arch in (‘armv6l’, ‘armv7l’):
player_args = [‘omxplayer’, ‘–vol’, ‘-6000’, uri]
player_kwargs = {‘o’: settings[‘audio_output’], ‘_bg’: True, ‘_ok_code’: [0, 124, 143]}