I noticed that the sounds used in the GUI isn't optimal for a several criteria: discretization, quantization, channels, volume and file size is too big.
I decided - 11025 Hz and 8bit will suffice without a visible quality lost.
See to the picture zabbix_sounds.png - it's discretization, quantization, channels improvement.
See to the picture zabbix_sounds_volumes_only.png - it's volume unification only.
New sounds in the archive. They are 6,2x small size that a original !!!
Only one file "alarm_disaster.wav" i left with the 22050 Hz discretization - because it has some hi frequency spectrum. But if you wont - even it can be down-sampled with the 11025 Hz
New sounds quality tested in the Sennheiser headphones with external DAC by optical connectivity
After, all sounds are tested successfully under 5 browsers.