Interference when using ROBOTEL SC2500 HS4S and SC2500 HS3S headsets

If you experience noise or electrical interference while using our headphones, here is some information that may help you troubleshoot the issue.

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By Fernando Solórzano

Creation date: 2022-04-04

Last update: 2023-02-16


The Robotel SC2500 HS3 and HS4 headsets have been specifically designed for professional use in language lab environments. The specifications of its electronic components are as follows:


• Headphone Characteristics:

• Frequency Response                                                   20Hz to 20KHz
• Impedance                                                                           2X 32ohms
• Sensitivity                                                                     97 dB SPL/1mW
• Continuous Power Rating                                                        100mW

• Microphone Characteristics:

• Type                                                                          Elektret condenser
• Frequency Response                                                 100 Hz to 20 KHz
• Impedance                                                                           ≤ 2.2 Kohms
• Sensitivity                                     -47 ± 3dBV (f – 1KHz, 0dB = 1 V/Pa)
• Sensitivity Reduction                                                                      -3 dB
• Signal to Noise ratio                                                                    56 dBA

• Connectors:

• Headset (HS4)                          combo TRRS 3.5mm mini phone plug

• Microphone (HS3)                        TRS 3.5mm mini phone plug (pink)

• Headphones (HS3)        stereo TRS 3.5mm mini phone plug (green)

• Dimensions:

• Cable length                                                            6.0 feet (1.8 meters)
• Weight                                                                         0.55 lbs (0.250 Kg)


When we refer to the speakers, our headphones have a closed acoustic behavior, that is, they isolate both external and internal sound from the outside. They are ideal for recording studios, or in our case, laboratory rooms. They have an excellent level of sensitivity, and their low impedance allows their efficient use in low consumption equipment such as mobile phones, tablets or personal players.


However, the value of impedance is relative, since while low impedance allows you to get good volume with almost any device, it is also important to remember that they can be more sensitive to interference or distortion.


When we refer to the microphone, it is a unidirectional condenser of the elektret type, which, without the need for a high supply voltage, lends itself to mobile devices, which must work with low battery voltages. Cell phones, laptops, tablets all use this type of microphone.

its high sensitivity value means that the microphone provides a high level of signal, that is, that the microphone is capable of picking up weak sounds. this microphone will therefore need less gain where we have it connected and therefore we will reduce the level of background noise.

Interference (Noise)

There are several approaches and methods you can try to correct static noise in your headphones when using them with a Windows computer:

  • Repair or update the version of your drivers.

  • Clean your headphone jack and port.

  • Check and (maybe) replace your power supply/CPU fan.

  • Check your electrical network.

  • Change the current audio format.

  • Disable all sound enhancements.

Repair or update the version of your drivers

Sometimes the root cause of static noise in headphones could be outdated or damaged drivers.

Clean your headphone jack and port

Regularly cleaning the audio jack on your headphones and the auxiliary port on your audio device can help prevent the buildup of dust and debris, which is actually one of the most common causes of static noise.

Simply take a cotton swab or Q-tip and slightly tear off the excess cotton until the wad is small enough to fit inside the aux port on your audio device. Lightly soak the cotton swab in isopropyl alcohol (preferably use control/contact/lubricant cleaner if you have one) and then clean the inside of the auxiliary port on your headphone's audio and playback jack.

Check and (maybe) replace your power supply/CPU fan

Static noises can occur when your computer gets too hot and requires more power to run than usual.

That's why replacing the old CPU fan to provide more effective cooling and/or replacing the power supply to give your computer more overall power can be a viable solution to get rid of buzzing or static noise from your headphones. .

Sometimes the noise comes from faulty or missing filter components in power supplies or current transformers (laptops). When the equipment is portable, it is always recommended to use the manufacturer's original transformers.

Check your electrical network

If the electrical network of the laboratory does not have adequate grounding, some of these excess currents can parasitize the audio signal, and in the medium-long term damage the sound card. It is advisable to verify the grounding capacity of the electrical network by a professional in the field.

Change the current audio format

There is also the possibility that the current audio output format is not optimal for the headphones you are using. Just change the audio format by following these easy steps. The static noise problem usually disappears when changing the audio format from 16-bit to 24-bit (remember, for Teacher LIVE, the sample rate should be kept at 44,100 Hz).

Disable all sound enhancements

Sound enhancements can also contribute to static noise in your headphones. Disabling them will allow you to get rid of the crackling or buzzing noises altogether. After navigating to the Advanced tab (Speaker Properties) and under Default Format, change the audio format. Click Apply and then OK.


Contact us if you would like more information.