Hi Nick,
I would like to ask these questions to assist you in a better way with this issue.
1) What is the exact model number of your Dell Inspiron 15 Laptop?
2) Does this happen with both the earphones and the external speakers which you connect through the 3.5 mm jack?
3) Are you able to hear this noise from the inbuilt laptop speaker?
4) Did you install the latest audio driver updates for the computer model from the Dell website and check the status?
This could be due to some issues with the audio drivers preinstalled on the computer. I would suggest you to try the following methods and check if that resolves the issue.
Method 1: Run the Playing Audio Troubleshooter
The Playing Audio Troubleshooter is an automated tool which checks for any common issues with the audio devices and its services. It also checks if the audio device on the computer is disabled and provide the detailed report of the audio device status.
a) Press “Windows Logo” + “W” keys from the keyboard.
b) Type “Troubleshooting” in the search bar and press “Enter”.
c) In the “Troubleshooting” window, click on “View All” on the left pane.
d) Click on “Playing Audio”.
e) Click on “Advanced” and then click on “Run as Administrator”.
f) Click “Next” and follow the on-screen instructions to complete the troubleshooting process.
Please check the troubleshooting report and let’s know the details. You may also try the suggestions given by the troubleshooter and check if that resolves the issue. If the issue persists, then try updating the sound card drivers on the computer from the Dell website and check if that helps.
Method 2: Update the Audio Drivers
Step 1: Check the Windows updates for any latest driver updates.
Check in Windows updates if any driver updates are available. If so, install the same and check if it helps.
a) Press “Windows Logo” + “W” keys from the keyboard.
b) Type “Updates” in the search bar and click on “Install optional updates” from the left pane.
c) From the “Windows Update” window, click on “Check for Updates” on the top left corner, to receive a fresh list of updates and then install all the updates listed there.
If there are no driver updates via Windows Update, then try the next method to update it from the Dell website.
Step 2: Update Driver Software from the Dell website
Go to the Dell or the Sound Card manufacturer’s website and search for the latest Windows 8 compatible driver available for the Sound Card model and then install it by following the instructions given in the website.
Hope this is helpful. Please get back to us with the troubleshooting results.