https://rudk.ws/2016/10/23/how-google-and-bing-protects-their-api/

bingy.rb

require 'open-uri'

class Bingy
  LANDING_PAGE = 'http://www.bing.com/translator'.freeze
  SPEAK_URL = LANDING_PAGE + '/api/language/Speak?locale=en-US&media=audio/mp3'

  def initialize(text, gender = 'male')
    @user_agent = 'User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36'
    @params = { text: text, gender: gender }
  end

  def params
    URI.encode_www_form(@params)
  end

  def url
    @url = SPEAK_URL + '&' + params
  end

  def cookies
    open(LANDING_PAGE, 'User-Agent' => @user_agent).meta['set-cookie']
  end

  def token
    cookies.scan(/(mtstkn=.+?);|(MUID=.+?);/).flatten.compact.join(';')
  end

  def request
    open(url, 'Cookie' => token,
              'Referer' => url,
              'Connection' => 'keep-alive',
              'Range' => 'bytes=0-',
              'Accept-Encoding' => 'identity;q=1, *;q=0',
              'Accept-Language' => 'en-US,en;q=0.8,uk;q=0.6')
  end

  def download(out)
    File.write(out, request.read)
  end
end