Try and catch, always catching exception

Question

what i am attempting to do is, get user input from a text box, convert it to an int and then use that. i got everything to work except the the try and catch. incase the person puts a letter instead of a number. with the code below it always catches something. i have no idea what is catches something. i've taken out the bool test and if i put in a letter it will just throw the exception then go to the beeping. other then waiting for a valid input. please excuse my messy code, i am still a beginner c# programmer :D thanks in advanced!

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication4
{
public partial class Form1 : Form
{
    bool tone = false;
    public Form1()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        bool test = true;
        speedInput.Clear();
        beep.Clear();
        int beepspeed = 90;
        int speed = 100;
        string speedtext = this.speedInput.Text;
        string beeptext = this.beep.Text;
        try
        {
            test = true;
            beepspeed = Convert.ToInt32(beeptext);
            speed = Convert.ToInt32(speedtext);
        }
        catch (Exception)
        {
            MessageBox.Show("numbers above 37 only!!");
            test = false;
        }

        if (test)
        {
            for (int i = 0; i < beepspeed; i++)
            {
                if (this.tone)
                {
                    Random ran = new Random();
                    int rand = ran.Next(400, 3000);
                    Console.Beep(rand, speed);
                }
                else
                {
                    Console.Beep(1000, speed);
                }
            }
        }
    }

    private void radioButtonYes_CheckedChanged(object sender, EventArgs e)
    {
        this.tone = true;
    }

    private void radioButtonNo_CheckedChanged(object sender, EventArgs e)
    {
        this.tone = false;
    }
}
}

Answer 1

You are cleaning the content of the inputs at the beginning of the button1_click

speedInput.Clear();
beep.Clear();

Then when you try to convert empty string to int32 it fails

beepspeed = Convert.ToInt32(beeptext);
speed = Convert.ToInt32(speedtext);