Display the formatted units on the volume setting.

android/res/values/strings.xml

         <string name="ssml">Load SSML Template</string>
         <string name="synthesis_demo">Enter text to speak:</string>
         <string name="espeak_volume">Volume</string>
+        <string name="formatter_wpm">%s WPM</string>
+        <string name="formatter_percentage">%s%%</string>
 
 </resources>

android/src/com/reecedunn/espeak/SpeechSynthesis.java

     /** Announce some of the punctuation characters. */
     public static int PUNCT_SOME = 2;
 
+    public enum UnitType {
+        Percentage,
+        WordsPerMinute,
+        /** One of the PUNCT_* constants. */
+        Punctuation,
+    }
+
     public class Parameter {
         private final int id;
         private final int min;
         private final int max;
+        private final UnitType unitType;
 
-        private Parameter(int id, int min, int max) {
+        private Parameter(int id, int min, int max, UnitType unitType) {
             this.id = id;
             this.min = min;
             this.max = max;
+            this.unitType = unitType;
         }
 
         public int getMinValue() {
         public void setValue(int value) {
             nativeSetParameter(id, value);
         }
+
+        public UnitType getUnitType() {
+            return unitType;
+        }
     }
 
-    /** Speech rate in words per minute. */
-    public final Parameter Rate = new Parameter(1, 80, 450);
+    /** Speech rate. */
+    public final Parameter Rate = new Parameter(1, 80, 450, UnitType.WordsPerMinute);
 
-    /** Audio volume in percent. */
-    public final Parameter Volume = new Parameter(2, 0, 200);
+    /** Audio volume. */
+    public final Parameter Volume = new Parameter(2, 0, 200, UnitType.Percentage);
 
-    /** Base pitch in percent. */
-    public final Parameter Pitch = new Parameter(3, 0, 100);
+    /** Base pitch. */
+    public final Parameter Pitch = new Parameter(3, 0, 100, UnitType.Percentage);
 
-    /** Pitch range in percent (monotone = 0). */
-    public final Parameter PitchRange = new Parameter(4, 0, 100);
+    /** Pitch range (monotone = 0). */
+    public final Parameter PitchRange = new Parameter(4, 0, 100, UnitType.Percentage);
 
-    /** Which punctuation characters to announce; see the PUNCT_* constants. */
-    public final Parameter Punctuation = new Parameter(5, 0, 2);
+    /** Which punctuation characters to announce. */
+    public final Parameter Punctuation = new Parameter(5, 0, 2, UnitType.Punctuation);
 
     public void synthesize(String text, boolean isSsml) {
         nativeSynthesize(text, isSsml);

android/src/com/reecedunn/espeak/TtsSettingsActivity.java

         pref.setOnPreferenceChangeListener(mOnPreferenceChanged);
         pref.setPersistent(true);
 
+        switch (parameter.getUnitType())
+        {
+            case Percentage:
+                pref.getExtras().putString("formatter", context.getString(R.string.formatter_percentage));
+                break;
+            case WordsPerMinute:
+                pref.getExtras().putString("formatter", context.getString(R.string.formatter_wpm));
+                break;
+            default:
+                throw new IllegalStateException("Unsupported unit type for the parameter.");
+        }
+
         pref.setMin(parameter.getMinValue());
         pref.setMax(parameter.getMaxValue());
 
                                 summary = entries[index].toString();
                             }
                         } else if (preference instanceof SeekBarPreference) {
-                            summary = (String)newValue;
+                            String formatter = preference.getExtras().getString("formatter");
+                            summary = String.format(formatter, (String)newValue);
                         }
-                        preference.setSummary(summary.replaceAll("%", "%%"));
+                        preference.setSummary(summary);
                     }
                     return true;
                 }