Try installing the DPC Latency Checker tool from
http://www.thesycon.de/deu/latency_check.shtml

This is a small app that is very easy to install, run, and interpret. If you see red spikes on the graph that coincide with the audio glitches, then there is excessive dpc latency, which most frequently is caused by a poorly written driver (usually not the audio driver). The  thesycon site gives an explanation of dpc latency and how to try to find a bad driver.


There is another tool. the LatencyMon:
http://www.resplendence.com/latencymon

It also checks for DPC latency and also checks ISR (interrupt Service Routines) and hard pagefaults. The site gives a good explanation of these.

Ok, so I downloaded the DPC Latency Checker tool and initially found yellow peaks every 5 seconds approximately, and red peaks fairly often as well.  When playing music or video, red peaks occur pretty frequently and usually coincide with the noises I hear.  These are also very high peaks - the maximum was 127570 microseconds.

However, I haven't been able to truly isolate the problem using device manager.  I used the site's suggestions, and don't have an internal modem or add on cards.  I progressively disabled my wireless N card, this family controller thing, intel display audio (not the realtek where sound comes from), and all USB devices.  The more turned off at the same time, the less severe the sound tends to appear, and the more level the green bars come, with no yellows.  However, the problem is still there, and red bars still do occur.  

It should be noted that when playing music or video, more subtle noises do not elicit a response from the DPC program, but the obvious ones really clearly do.

As a side note, does this confirm it is a software problem?

Do you have any suggestions for what other drivers I can try to turn off without losing functionality?  As a semi last resort is there a way to automatically run through something which uninstalls most drivers and then reinstalls them, so as not to lose functionality in the process of manually doing it click by click?  Could it still not be drivers?  I'm finding it odd that the more drivers disabled, the less severe the speaks become, and the less overall severe the noise is, yet the problem still clearly remains.  Thanks!

Addendum to Previous Post:

In addition, I used the LatencyMon program.  This did not detect nearly as many DPC's and no peaks or anything while running DPC Latency Checker at the same time, which still was detecting peaks.  It does say "some processes were hit by hard pagefaults. If these were programs producing audio, they are likely to interrupt the audio stream resulting in dropouts, clicks and pops. Check the Processes tab to see which programs were hit."  The hardest hit was windows media player and peak was 475997.  I don't know if that makes a difference though.

The following drivers had ISR and DPCs, with ISR the number on the left and DPC the number on the right.  I don't know if this will give any info on which drivers are affected though, and not sure which are save to disable (the largest values I bolded, and the really largest italicized as well, one I'm curious about one that I italicized since there's no description given for what the driver is, which happened with a few, but still seemed weird, though guessing now reading it it's probably the other latency program running in the background):

ACPI.sys - ACPI Driver for NT -  ISR 5184 / DPC 15176

afd.sys - Ancillary Function Driver for WinSock - 0 / 83256

CLASSPNP.SYS - SCSI Class System Dll - 0 / 37576

cng.sys - Kernal Cryptography Next Generation - 0 / 2430

dxgkrnl.sys - DirectX Graphics Kernel - 0

dpclat_driver.sys - No Description Given? - 0 / 11576597

/ 901680

hal.dall - Hardware Abstraction Layer DLL - 11717961 / 0

HDAudBus.sys - High Definition Audio Bus Driver - 1239298 / 1222103

HECIx64.sys - Intel (R) Mangement system interface - 508 / 12183

HTTP.sys - HTTP Protocol Stack - 0/ 2713

iaStor.sys - Intel Rapid Storage Technology driv... 2150773 / 2210860

igdkmd64.sys - Intel Graphics Kernel Mode Driver - 0 / 11756

luafv.sys - LUA File Virtualization Filter Driver - 0 / 792

ndis.sys - 0 / 466348

netbt.sys - MBT transport driver - 0/4495

NETIO.SYS - Network I/O Subsystem - 0/54049

ntfs.sys - NT File System Driver - 0/1272

ntoskrnl.exe - NT Kernel and System - 0/499407

nvlddmkm.sys - NVIDIA Windows Kernal Mode Drive... - 0/128791

rdbss.sys - Redirected Drive Buffering SubSyst... 0 / 790

srv.sys - server driver - 0/9540

srvnet.sys - server driver - 0/9540

tcpip.sys - TCP/IP driver - 0/70131

tunnel.sys - microsoft tunnel interface driver - 0/23444

usbccgp.sys - USB Common Class Generic Parent... 0/2782

wdf01000.sys - kernel mode driver framework runt... 0/11677

-------------------

idk if this means anything, or if the pagefaults thing makes a difference.  Could it not be a driver, but a program as well?

I am not a computer guru and can't answer most of your questions. I 'm more like a sort of historian, I guess. I suggested checking for excessive dpc latency to try to answer your question about whether it could still be the hardware. Since Dell uses refurbished parts then sure it could be the hardware, but in my mind the fact that you get spikes simultaneously with the audio distortion points to a software issue.

Could it not be a driver, but a program as well?

The only thing I know that can cause excessive dpc latency is a bad driver -- but -- here's where the history comes in. A tech said that your noise reminded her of the problems with the Studio's. This happened a couple of years ago. The main models that were affected at that time were the Studio 1735, Studio 1737, Studio 1535, Studio 1537, and Studio XPS 1340, and some Vostro models. Perhaps Studio 1555 also.

Dell came up with a BIOS revision that fixed the excessive dpc latency on the Studio XPS 1340 model, as long as the units were configured with Intel WLAN cards and not Dell (Broadcom) cards. (The drivers for the cards produced excessive dpc latency in addition to the latency being produced by whatever the BIOS fixed -- I never learned what it was.) Encouraged by that success, the engineers plan was to get a BIOS fix for  the Studio 1737 and then apply that knowledge toward a fix for the other models, but that never happened. Two different BIOS were released in the following months to fix the problem but each was a big flop. Finally the engineers said that the 1737 has a design limitation that prevents latency issues from being resolved, and then they gave up trying to fix it. (This was a remarkable period in the history of Dell laptop audio, because usually they never try to fix audio problems, just release a newer model instead.)

The point is that the team said it was a hardware problem that they could not fix because the problem was already designed in. However that excuse was met with scepticism by the Studio owners who thought it was just a cop out. But because the engineers implied that there was a hardware issue, I cannot say definitively that only a bad driver can cause excessive dpc latency, but that is what I will believe until shown otherwise.

Anyway, those were the only models that had excessive dpc latency that could not be resolved. Other models since then have had it but driver updates and such have fixed it. Your model apparently did not have it until something changed last week, maybe a Microsoft update of something like that.

I can't really answer your other specific questions. Even the sycon site says that turning off drivers might not let you find the source of the problem. Or sources, as there could be multiple ones.

Using the second latency tool im getting alot of hard pagefaults as well.... with searchprotocolhost, searchindexer, and svchost

I am also having this problem! It just started in the last couple days. I get the short audio freezes and shorter stumbles. I did the latency test and get the odd yellow spike (1000us) and this corresponds with an audio freeze. I also tried updating all my drivers to no avail...

I'm thinking a recently installed program (Altium) might have changed something? Or my hard drive is starting to fail?  

My laptop is dell l501x with i7 1.7Ghz, 6gb ram, 500g hd

Any progress???

Ok I couldn't handle it anymore and thought it would be easier/quicker to simply reinstall windows..... IT WORKED! No more glitchy or skipping music. Using both of those latency tools however still shows lots lof latency. The first tool now shows a red bar every 5-6 seconds but there are no glitches in audio.  

The only downside is that it took me ALLLLLLL Day to reinstall windows. Dell recovery is garbage.

-hard drive recovery partition did not work so I used a backup cd i made (with dell datasafe)

-backup cd appeared to freeze but i left it alone for a while.. When i came back I was just about to hit the power button and it immidietly jumped from the stuck 41% to complete..... needless to say it didnt complete anything except screwing up my hd

-now i got a "remove media or disk and restart" error in dos upon trying to  reboot into windows... So the only thing i could do is insert the cd and try the backup again.. I tired the format option as well as the regular restore options several times and none of them worked.

-so i figured maybe i had an old vista or xp cd kicken around so i could get into windows to downalod a win7 image from the net and do a clean install... but I didnt... but luckily I found a later backup cd i made but forgot about

 SO, make sure you have atleast 3 backup sources ready (2 will probably fail if they're Dell) and preferebly a windows iso cd before you attempt to reinstall win7

problem solved though ..

I solved this problem disabling the desktop gadgets that was checkings elementes of hardware (cpu freq, nvidia temps..) Try this if you have this gadgets on your desktop.

please help i have the same problem, I have warranty remaining still 6 months.. when i called they asked to re-install windows and i did and still the problem exists.. please please help someone

I have warranty remaining still 6 months.

You have had this problem the whole time, ever since you first started up the laptop, or did the problem show up later?