Use shortest frequency unit

index.js

@@ -197,6 +197,9 @@ var wringValue = function (prop, value) {
   ).replace(
     re.angle,
     toShortestAngle
+  ).replace(
+    re.freqEndsWithThreeZeros,
+    "$1$2kHz"
   ).replace(
     re.urlFunction,
     unquoteURL

lib/regexp.js

@@ -29,6 +29,9 @@ re.descriptorFontFace = /^font-(style|stretch|variant|feature-settings)$/i;
 // \(, \)
 re.escapedBraces = /\\([()])/g;
 
+// 1000Hz
+re.freqEndsWithThreeZeros = /(^|\s|\(|,)(\d+)000Hz/gi;
+
 // /**/, /*\**/
 re.hackPropComment = /\/\*(\\\*)?\*\//;
 

test/expected/freq.css

@@ -0,0 +1 @@
+.foo{pitch:12kHz}

test/fixtures/freq.css

@@ -0,0 +1,3 @@
+.foo {
+  pitch: 12000Hz;
+}