diff --git a/lib/routes/api/tts-cache.js b/lib/routes/api/tts-cache.js
index 9a0ff99..fb46559 100644
--- a/lib/routes/api/tts-cache.js
+++ b/lib/routes/api/tts-cache.js
@@ -9,6 +9,7 @@ const {DbErrorBadRequest} = require('../../utils/errors');
 const Account = require('../../models/account');
 const sysError = require('../error');
 const { getSpeechCredential, decryptCredential } = require('../../utils/speech-utils');
+const PCMToMP3Encoder = require('../../record/encoder');
 
 router.delete('/', async(req, res) => {
   const {purgeTtsCache} = req.app.locals;
@@ -38,6 +39,7 @@ router.post('/Synthesize', async(req, res) => {
   try {
     const accountSid = parseAccountSid(req);
     const body = req.body;
+    const encodingMp3 = req.body.encodingMp3 || false;
     if (!body.speech_credential_sid || !body.text || !body.language || !body.voice) {
       throw new DbErrorBadRequest('speech_credential_sid, text, language, voice are all required');
     }
@@ -85,18 +87,31 @@ router.post('/Synthesize', async(req, res) => {
       disableTtsCache: false
     });
 
-    const stat = fs.statSync(filePath);
+    let contentType = 'audio/mpeg';
+
+    let readStream = fs.createReadStream(filePath);
+    if (['nuance', 'nvidia'].includes(cred.vendor) ||
+      (
+        process.env.JAMBONES_TTS_TRIM_SILENCE &&
+        ['microsoft', 'azure'].includes(cred.vendor)
+      )
+    ) {
+      if (encodingMp3) {
+        readStream = readStream
+          .pipe(new PCMToMP3Encoder({
+            channels: 1,
+            sampleRate: 8000,
+            bitRate: 128
+          }, logger));
+      } else {
+        contentType = 'application/octet-stream';
+      }
+    }
     res.writeHead(200, {
-      'Content-Type': 'audio/mpeg',
-      'Content-Length': stat.size,
+      'Content-Type': contentType,
     });
-
-    const readStream = fs.createReadStream(filePath);
-    // We replaced all the event handlers with a simple call to readStream.pipe()
     readStream.pipe(res);
-
     readStream.on('end', () => {
-      // Delete the file after it's been read
       fs.unlink(filePath, (err) => {
         if (err) throw err;
         logger.info(`${filePath} was deleted`);
diff --git a/lib/swagger/swagger.yaml b/lib/swagger/swagger.yaml
index 15c1321..0c3588d 100644
--- a/lib/swagger/swagger.yaml
+++ b/lib/swagger/swagger.yaml
@@ -4320,6 +4320,10 @@ paths:
                   type: string
                   description: voice ID
                   example: en-US-Standard-C
+                encodingMp3:
+                  type: boolean
+                  description: convert audio to mp3.
+                  example: true
               required:
                 - speech_credential_sid
                 - text