Ustadh, In Manhaj as Salikeen Book of Prayer it´s stated that laughing invalidates the Salah. Does this mean laughing with sound/long time or even just quietly ? As example someone frequently makes Du´a to get married and have children and remembers his nephew and how cute he acted and laughs.

Ustadh AbdulAziz al-Haqqan

The ulama mentioned laughing that sound is heard from and they specify when 2 letters r heard as for just smiling it doesn't nullify the salah some even mentioned that laughing without a sound doesn't nullify it but my question is where is the khushu' in the salah!