Described are a gradient system and method, wherein at least two fluids are mixed in accordance with a noise level threshold. An inlet receives the fluids. A pump head body has a mixing chamber therein in communication with the inlet. The mixing chamber has a first delay volume configured to mix the fluids having a noise level. A pump head extension has a mixing chamber extension therein extending from the mixing chamber. The mixing chamber extension increases the volume of the mixing chamber by a second delay volume to a third delay volume. The fluids are mixed in the third delay volume at a compositional noise level that is less than the noise level.