Audio crackling is the sound of the audio stream breaking up, and it usually comes from the sample rate, audio enhancements, or another driver delaying the audio pipeline. It is rarely the speakers themselves, so test with different outputs before replacing hardware.
Fix it, in order
Test another output. Try headphones, then speakers, then a USB headset. If only one output crackles, that device or its connection is the problem. If all of them crackle, the problem is in Windows audio itself.
Change the sample rate and bit depth. Open Settings, System, Sound, select the output device, and under Output settings set Format to 2 channel, 16 bit, 48000 Hz. Higher rates such as 192000 Hz can crackle on drivers that do not handle them well, and 48000 Hz is the most compatible setting.
Turn off audio enhancements. In the same device settings, turn off audio enhancements. Enhancements such as bass boost and virtual surround process the stream in real time, and a buggy enhancement is a classic cause of popping.
Disable exclusive mode. Open the device properties, go to the Advanced tab, and uncheck Allow applications to take exclusive control of this device. An app changing the format underneath other apps causes exactly this kind of crackle.
Update the audio driver. In Device Manager, expand Sound, video and game controllers, right-click the audio device, and select Update driver. If the crackling started after an update, use Roll Back Driver on the Driver tab instead, or install the driver from the PC maker's site.
Switch to the High performance power plan. Open Control Panel, Power Options, and select High performance for testing. Power saving states can delay the CPU just enough to starve the audio stream, and the crackle vanishing on High performance confirms it.
Update the Wi-Fi and Bluetooth drivers. On many laptops, an outdated wireless driver causes the audio delays that sound like crackling. Install the latest wireless driver package from the PC maker's site.
Try a different port or cable. For wired audio, a damaged cable or a loose jack crackles with every movement. Swap the cable and try another port before blaming Windows.
Crackling that only happens in one app is that app's problem, not Windows. Check the app's own audio settings and output device first, since reinstalling the system driver will not fix a single app.
If it still happens
If the crackle follows the same audio device to another PC, the device or its cable is failing. If it happens on every output on this PC only, and survives a driver reinstall, the cause is usually a misbehaving driver elsewhere in the system, and updating the chipset and wireless drivers from the PC maker's site is the next step before considering a Windows repair install.
Common questions
Why does audio crackle only in one app? That app is using a different sample rate or holding exclusive control of the device. Check the app's audio settings, and turn off exclusive mode in the device properties so no app can change the format for the rest.
Crackling started after a Windows update. What changed? The update likely replaced the audio driver or changed the default format. Rolling the driver back or setting the format to 2 channel, 16 bit, 48000 Hz are the two fastest fixes.
Does a higher sample rate sound better? Not on most hardware, and it can cause crackling if the driver cannot keep up. For everyday listening, 48000 Hz is the safe setting, and the difference from higher rates is inaudible on typical speakers and headphones.