Configure flycheck to make a "ding!" sound after it completes checking, only in certain modes

Ding.el

  ;; Noisy Flycheck (for slow syntax checkers, program verifiers, &c.)
  (defvar flycheck-ding t)                                    ;; Enable sounds?
  (defvar flycheck-ding-path "~/.emacs.d/private/Ding.mp3")   ;; Where's the "ding!" sound to make?
  (defvar flycheck-buzz-path "~/.emacs.d/private/Basso.aiff") ;; Where's the "bzz!" sound to make?
  (defvar flycheck-noisy-modes-list '(dafny-mode))            ;; Which modes should we make sounds in?

  ;; Below what number of seconds checking time should we be silent?
  (defvar flycheck-ding-delay-threshold 2)
  (defvar flycheck-buzz-delay-threshold 1)

  (defun play-sound (sound-file)
    (call-process-shell-command
      (concat "afplay " sound-file " &> /dev/null") nil 0))

  (defun flycheck-ring-bell ()
    (if flycheck-ding
        (if (member major-mode flycheck-noisy-modes-list)
            (lexical-let*
                ((errors-exist (flycheck-has-current-errors-p 'error))
                  (sound-file (if errors-exist
                                  flycheck-buzz-path
                                  flycheck-ding-path))
                  (elapsed-time (- (float-time) flycheck-start-time)))
              (progn
                (setq flycheck-total-time (+ flycheck-total-time elapsed-time))
                (if (> flycheck-total-time
                        (if errors-exist
                            flycheck-buzz-delay-threshold
                            flycheck-ding-delay-threshold))
                    (progn
                      (setq flycheck-now-running nil)
                      (run-with-timer
                        0.05 nil
                        (lambda () (if (not flycheck-now-running)
                                  (progn
                                    (setq flycheck-total-time 0)
                                    (play-sound sound-file))))))))))))

  (defun flycheck-register-start-time ()
    (progn
      (if (not (boundp 'flycheck-total-time))
          (defvar flycheck-total-time 0))
      (if (boundp 'flycheck-start-time)
          (setq flycheck-start-time (float-time))
          (defvar flycheck-start-time (float-time)))
      (if (boundp 'flycheck-now-running)
          (setq flycheck-now-running t)
          (defvar flycheck-now-running t))))

  (add-hook 'flycheck-before-syntax-check-hook 'flycheck-register-start-time)
  (add-hook 'flycheck-after-syntax-check-hook 'flycheck-ring-bell)