Ratheth. Depends where the noise is coming from.
If from IBL shown as background image. Via TA firewall. Put gels inside to light the scene.
If from small light sources within the render environment, stimulated by IBL inside background link (the obscure approach). Half IBL effect and put radials inside the light sources. The mix of direct and indirect will increase render time but will also reduce noise. Sometimes you can get away with turning cast shadows off for these lights.
If black fireflies. The issue is possibly inverted normals in a model - try using mesh smooth options in Bryce, sometimes that does the trick.
If white fireflies. Check out reflective surfaces, if combined with diffuse, the light can multiply and cause a problem.
Failing all else, render very large and use noise cancellation in a paint package. Then reduce the size of the render to mitigate the effect of noise cancellation - which can leave artefacts.