Remove hum when recording sounds

To remove the mains electricity hum when recording with Snooper, you can apply a pre-recording filter. The hum is usually present at frequency 50 Hz or 60 Hz so a high-pass filter or a notch filter should be fine.

Removing the hum would significantly improve the quality of the recording and make triggering more accurate.

Measuring the frequency distribution with the built-in frequency analyzer with no filter shows:

Frequency analyzer – no filter

Set the filter to a high-pass filter with a cutoff-frequency of 200 Hz.


This will attenuate the hum at 50 Hz and the harmonic at 100 Hz with approximately 20 dB.

Frequency analyzer – high-pass 200Hz


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Flicker free TableLayoutPanel

If you are using the TableLayoutPanel from the .NET framework and want to reduce the flickering when resizing, you could enable double-buffering by sub-classing the TableLayoutPanel class.

When double buffering is enabled, all paint operations are first rendered to a memory buffer instead of the drawing surface, this will heavily reduce flickering.

Replace any references to the TableLayoutPanel with reference to the newly created TableLayoutPanelDoubleBuffered class.

public class TableLayoutPanelDoubleBuffered : TableLayoutPanel
        public TableLayoutPanelDoubleBuffered()
            this.DoubleBuffered = true;

Handling collections in PropertyGrid

To detect if the collection editor for the .NET PropertyGrid has the OK or Cancel button clicked you can use the below code and subscribe to the MyFormOK or MyFormCancel events.

public class MyCollectionEditor : CollectionEditor
       public delegate void MyFormClosedEventHandler(object sender, FormClosedEventArgs e);
       public delegate void MyFormCancelEventHandler(object sender);
       public static event MyFormClosedEventHandler MyFormOK;
       public static event MyFormCancelEventHandler MyFormCancel;

       private bool cancel;

       public MyCollectionEditor(Type type) : base(type) { }

       protected override CollectionForm CreateCollectionForm()
           CollectionForm collectionForm = base.CreateCollectionForm();
           collectionForm.FormClosed += new FormClosedEventHandler(collection_FormClosed);
           cancel = false;
           return collectionForm;
       protected override void CancelChanges()
           if (MyFormCancel != null)
           cancel = true;

       void collection_FormClosed(object sender, FormClosedEventArgs e)
           if (MyFormOK != null && !cancel)
               MyFormOK(this, e);


Activate the enhanced MyCollection editor:

[Editor(typeof(MyCollectionEditor), typeof(UITypeEditor))]
public List<Person> UserList { getset; } = new List<Person>();

Snooper Professional with two tone triggering

New version of Snooper Professional 2.2.3.

It’s now possible to use frequency triggering with Snooper Professional.

Four different modes to choose from:

  • Two-Tone Sequential – Triggers on a Two tone paging signal.
  • Single tone – Triggers on a single frequency.
  • Dual tone – Triggers on two combined tones.
  • DTMF sequence – Triggers on a series of DTMF tones.

Many pagers and control systems use some sort of audio tones to activate. The most common type are two tones that are sent in sequence, mostly referred to as Two-Tone Paging or Two-Tone Sequential.

Using Snooper Pro it’s very easy to setup a recording that is triggered by a Two-tone sequence.

Snooper Professional


Run Snooper as a service

A great thing about Snooper sound recorder, it can be executed as a Windows service. When this feature is enabled, the Snooper program will start recording when the computer boots up, even if no user logs in.

Before settings this up, check that you have the Pro version installed. Only the Pro version can be installed as a Windows service.

To setup Snooper to run as a service follow these steps:

In the General tab press the “Start by service…” button and fill in the credentials for the user whom the Snooper is configured for. Check the “Enable Snooper Professional service” checkbox. This will actually install the program as a Windows service, uncheck if you want to uninstall the service.

Note! The account running the service must be password protected or service installation will fail.

Press close.

Snooper service setup

If you want the service to start recording when the service is started, remember to check the “Start recording in selected mode” checkbox. If you only have scheduled recordings, you can uncheck this. “Start when windows starts” checkbox should be unchecked.

The recording begins when the service starts

Setup was made with Snooper Professional version 1.15.4

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