High-pressure sodium discharge lamp

A high-pressure sodium discharge lamp provided with an elongate discharge vessel which encloses a discharge vessel which encloses a discharge path and which vessel has an effective length L.sub.e and, over at least 2/3 of the discharge path a cross-section S of constant area, in which vessel two electrodes are arranged each having an end, between which ends the discharge path extends, said lamp being operative with a power of periodically alternating value, this power comprising one or more power components sinusoidally varying with time and at least one component having a frequency .nu..sub.i for which it holds that i-0.45.ltoreq.2.35.nu..sub.i Le/c.ltoreq.i+0.45, where i is an integral positive number and c is the average speed in m/s of propagation of sound waves through the gaseous part of the filling of the discharge vessel in the operative condition of the lamp, characterized in that the filling in the operative condition has a pressure P of at least 170.times.10.sup.3 Pa and in that for each value of i the relation M.nu..sub.i .multidot.f.sub.i .multidot.P.multidot.d.ltoreq.185 is satisfied, in which M.nu..sub.i is the modulation depth of the power component frequency .nu..sub.i, f.sub.i is a geometric lamp factor and d is the mean inner diameter of the cross-section S in meters.