diff --git a/lib/middleware.js b/lib/middleware.js
index 6c7f2644..0e214de9 100644
--- a/lib/middleware.js
+++ b/lib/middleware.js
@@ -235,7 +235,20 @@ module.exports = function(srf, logger) {
       }
       /* retrieve the application to execute for this inbound call */
       const params = Object.assign(['POST', 'WS'].includes(app.call_hook.method) ? {sip: req.msg} : {},
-        req.locals.callInfo);
+        req.locals.callInfo, {
+          defaults: {
+            synthesizer: {
+              vendor: app.speech_synthesis_vendor,
+              language: app.speech_synthesis_language,
+              voice: app.speech_synthesis_voice
+            },
+            recognizer: {
+              vendor: app.speech_recognizer_vendor,
+              language: app.speech_recognizer_language
+            }
+          }
+        });
+      logger.debug({params}, 'sending initial webhook');
       const obj = rootSpan.startChildSpan('performAppWebhook');
       span = obj.span;
       const b3 = rootSpan.getTracingPropagation();