control amplitude threshold via UI

index.html

@@ -10,6 +10,7 @@
     <div class="panels">
       <div>
         Bit Duration: <input id="bit-duration-text" type="number" min="0" max="1000" value="180">ms<br>
+        Amplitude Threshold: <input id="amplitude-threshold-text" type="number" min="0" max="255" value="200"><br>
         <input type="text" id="text-to-send">
         <button id="send-button">Send</button>
         <h2>Sent</h2>

index.js

@@ -38,7 +38,11 @@ function handleWindowLoad() {
     FREQUENCY_DURATION = parseInt(event.target.value);
     bitSampleCount = 0;
     samplesPerBit.length = 0;
-  })
+  });
+  document.getElementById('amplitude-threshold-text').addEventListener('input', (event) => {
+    FREQUENCY_THRESHOLD = parseInt(event.target.value);
+  });
+  
 
   // wire up events
   sendButton.addEventListener('click', handleSendButtonClick);