turn down
• adjust a control on a device to reduce the volume or level.
• "she turned the sound down"
Opposite:
turn up,
• reject something offered or proposed.
• "his novel was turned down by publisher after publisher"
turndown
noun
• a rejection or refusal.
• "no idea should meet a flat turndown if there's a chance of a pay-off"
• a decline in something; a downturn.
• "the company has suffered a dramatic turndown after a storm of bad publicity"
turndown
adjective
• (of a collar) turned down.