public function getHeaders()
    {
        $this->getOptions()->getAuthenticate()->setPostData($this->getPayload());

        $headers = [
            'Content-Type: application/json',
            'Host: tts.eu-west-1.ivonacloud.com',
            'User-Agent: ' . $this->getOptions()->getUserAgent()
        ];

        return array_merge(
            $headers,
            $this->getOptions()->getAuthenticate()->getHeader(self::SERVICE_TYPE_SPEECH)
        );
    }