How do I eliminate relay noise?

I would like to put an RC network across the relay coil to reduce relay noise, is there any formula to calculate the value of Resistance, Capacitance and their current and voltage values?

If you are experiencing relay noise in your HI 2151/30WC, HI 2160RC, or some of our older model weight controllers you can install a "snubber" to help reduce the noise levels. In most cases, RC snubbers with a value of 220 ohm resistor and .01uF capacitor will work fine because most of our relays are limited to 4 amps and 120/230 vac. Selection of the Resistor and Capacitor values to help stop the collapsing field from interfering with the weight controller is as follows:

A guide in selecting R and C values would be:
R= 0.5 to 1 ohm per 1v contact voltage.
C= 0.5 to 1uF per 1 Amp of contact current.

Values can vary depending on the properties of the load and variations in the relay characteristics. Typical values for a 115 volt circuit are 220 ohms for the resistor and 1 micro farad for the capacitor.

Capacitor (C) acts to suppress the discharge the moment the contacts open. Resistor (R) acts to limit the current when the power is turned on the next time. Use a capacitor with a break down voltage of 200 to 300V. Use AC type capacitors (non-polarized) for AC circuits.

For DC relays, the diode connected in parallel with the coil causes the energy stored to flow to the coil in the form of current and dissipates it as joules heat as the resistance component of the inductive load. This circuit further delays the release time. Use a diode with a reverse break down voltage at least ten times the circuit voltage and a forward current at least as large as the load current. In an electronic circuit where the circuit voltages are not so high, a diode can be used with a reverse breakdown of about 2-3 timer the power supply voltage.