How to fade in and fade out led strip connected to arduino based on continous analog input from capacitative sensor?
Smooth the change in output value by taking, e.g 10% of the new value, and 90% of the old value. You can try experimenting with different ratios and longer/shorter delays.

int lastValue = 0;

{
  Serial.println(value1);//value that i get from analog sensor
  //this is just to get the values in order for the led and sound
  if (value1&lt;=8) value1=-100;
  value1 = (1*value + 9*lastValue)/10;// smooth the change in value by taking 10% of the current value, and 90% of the previous value
  analogWrite(ledPin,value1+100);//these weird calculations seem to work for me
  tone(tonepin,value1+100,100); 
  lastValue = value1;
  delay(10);