Kling 3 sound on or off: $0.07 a second extra, when it pays

Turning sound on for kling-3 adds $0.07 per second on Sume: $0.14 silent, $0.21 with audio. A 10-second clip is $1.40 or $2.10. The flag is generate_audio, and the catalog default is on, so you only save money by sending false.

The difference per clip

The extra is linear in length, so the premium for sound on a 15-second clip is three times the premium on a 5-second one.

Silent plus your own bed

If you were going to replace the sound anyway, compare two routes. A 10-second silent clip is $1.40. A music generation is $0.125 per audio and a Timeline render is $0.10 per output minute (rounded up), so a silent clip with a music bed and a Timeline join lands near $1.63, against $2.10 for the clip with built-in sound.

The silent route is about $0.47 cheaper in that case, at the price of two more jobs to track. It also wins when you want to control the track: your own music, your own voice, or a licensed bed. If the clip would go out with its built-in sound as it is, the single job at $2.10 is simpler.

Set it explicitly

Send the flag every time so a default never changes your bill.

{
  "model": "kling-3",
  "prompt": "Hands wrap a gift, close-up, warm lamp light",
  "duration": 10,
  "generate_audio": false
}

A rule of thumb

Leave sound on when the clip is going out as it is: a social post, a product loop with ambient noise, a draft you want to judge as a viewer would. Turn it off when a voiceover, a licensed track or a platform sound will replace it, because you would pay for audio you discard.

Sume reserves the full price at submit, so the clip price must be free in the balance when you send the request. If it is not, the call fails with 402 insufficient_credits before any provider work starts.

• Testing prompts: silent is enough, and 33% cheaper per clip.
• Final render with ambience: sound on.
• Final render under a voiceover: silent.