Try running watch -n1 -d cat /proc/interrupts and look for the line identifying snd_intel_hda:card0 on the right. For me it’s IRQ 16, and goes up by around 350 interrupts per second on CPU 6.
CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 CPU6 CPU7
1: 0 0 82338 0 0 0 0 0 IR-IO-APIC 1-edge i8042
8: 0 0 0 0 0 0 0 0 IR-IO-APIC 8-edge rtc0
9: 0 435474 0 0 0 0 0 0 IR-IO-APIC 9-fasteoi acpi
12: 0 280 0 0 0 0 0 0 IR-IO-APIC 12-edge i8042
14: 0 0 0 0 503446 0 0 0 IR-IO-APIC 14-fasteoi INT34C5:00
16: 0 0 0 0 0 0 7505306 0 IR-IO-APIC 16-fasteoi intel_ish_ipc, i801_smbus, snd_hda_intel:card0
27: 0 0 0 0 0 0 0 0 IR-IO-APIC 27-fasteoi idma64.0, i2c_designware.0
30: 0 0 0 0 0 0 9337572 0 IR-IO-APIC 30-fasteoi idma64.2, i2c_designware.2
40: 0 0 0 0 0 87 0 0 IR-IO-APIC 40-fasteoi idma64.1, i2c_designware.1