Method for operating a discharge lamp and discharge lamp

A lighting apparatus comprising

• a discharge lamp which is operated with at least two different frequencies, each of which is addressed for a certain number of periods, wherein the discharge lamp comprises an arc tube with a pair of electrodes,
• a ballast unit for providing a current signal for the discharge lamp, and
• a control unit that is configured to
• define at least one probability distribution function for a first number of first frequency periods and a second number of second frequency periods,
• determining the first number of first frequency periods and the second number of second frequency periods depending on the probability distribution function by at least one random number, and
• modulate the current signal by applying the first number of first frequency periods and the second number of second frequency periods to the current signal for operating the discharge lamp;
• wherein
• a frequency period contains at least two commutations where the polarity of the current signal is changed, and
• the probability distribution function is defined as a probability density function with a corresponding cumulated density function and the first and second numbers for the first and second frequency periods are determined by applying the at least one random number to a corresponding inverse function of the cumulated density function.