Clear value for searchable dropdown when no results found using typeahead

I have three fields Name, Dept. and Title where Name is a Searchable dropdown field. Dept. and Title are read only fields. I want to be able to clear the fields Dept. and Title when no results are returned for Name.

First I selected test,test from the dropdown list under Name. After I select it, then the Dept. and Title show up.

If I change the Name and get no result (None found), I want to clear Dept and Title fields. How can I do that?

Here is my code

 <script>

                var Speakers = new Bloodhound({
                    datumTokenizer: Bloodhound.tokenizers.obj.whitespace('value'),
                    queryTokenizer: Bloodhound.tokenizers.whitespace,
                    limit: 10,
                    remote: {
                        url: '/AJAX/searchspeakers?q=%QUERY&searchType=Speakers',
                        rateLimitWait: 250,
                        ajax: { cache: false }
                    }
                });

            Speakers.initialize();

                var setupTypeAhead = function (target) {

                    $(target + '_Name').typeahead(null, {
                        name: 'Speakers',
                        display: 'Name',
                        source: Speakers.ttAdapter(),
                        minLength: 3,
                        highlight: true,
                        templates: {
                            empty: [
                                '<div class="empty-message">',
                                'None found...',
                                '</div>'
                            ].join('n'),
                            suggestion: Handlebars.compile('<div><strong>{{Name}}</strong><br>{{Extra}}</div>')
                        }
                    }).on('typeahead:selected typeahead:autocompleted', function (obj, selected, name) {
                        $(target + '_Name').val(selected.Contact.Name);
                        $(target + '_Dept').val(selected.Contact.Dept);
                        $(target + '_Title').val(selected.Contact.Title);
                    }).off('blur', function () {
                        $this('close');
                    });
                }


        </script>