After we flush our downstairs commode the pipes rattle. What causes this and how can we fix it?

After we flush our downstairs commode the pipes rattle. What causes this and how can we fix it?
Please explain a little more in detail. Describe the sound. Is it a deeper sound such as you would hear from the drain as the discharge goes down? This would point toward the drainage. Is is a rattling sound like a water pipe that's not strapped securely? Let me know, Tom

It is a loud vibrating noise that sounds like something is loose. When it happens we go up stairs and turn the shower on the bathroom sink faucet on to get the noise to stop. The other water running lessen the rattling and sometimes stops. Someone told me that we have an air bubble in the line. Could this be true?

You are more likely to have doctors changing bed pans than having air in your lines. You have a loose washer, either in the toilet fill valve or the stop valve under the toilet tank. I'm going to say it's the stop valve. You can remove the stem and tighten the washer but you are probably better off replacing the valve. Turn the water to the house off. Remove the supply tube that goes up to the toilet tank. Put one wrench on the body of the valve and another on the nut around the pipe. Unscrew the nut, pull the valve off, put new valve on and tighten the nut. You won't be using the nut and brass ring that came with the new valve.

Open the toilet water supply valve (angle stop) all the way...

Thank you that fixed it.;) :)