diff --git a/app/models/user.rb b/app/models/user.rb
index 868920364..b30329d13 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -46,8 +46,8 @@ class User < ApplicationModel
   belongs_to              :organization,   inverse_of: :members
 
   before_validation :check_name, :check_email, :check_login, :check_mail_delivery_failed, :ensure_uniq_email, :ensure_password, :ensure_roles, :ensure_identifier
-  before_create   :check_preferences_default, :validate_ooo, :domain_based_assignment, :set_locale
-  before_update   :check_preferences_default, :validate_ooo, :reset_login_failed, :validate_agent_limit_by_attributes, :last_admin_check_by_attribute
+  before_create   :check_preferences_default, :validate_preferences, :validate_ooo, :domain_based_assignment, :set_locale
+  before_update   :check_preferences_default, :validate_preferences, :validate_ooo, :reset_login_failed, :validate_agent_limit_by_attributes, :last_admin_check_by_attribute
   after_create    :avatar_for_email_check
   after_update    :avatar_for_email_check
   before_destroy  :avatar_destroy, :user_device_destroy, :cit_caller_id_destroy, :task_destroy
@@ -1001,6 +1001,22 @@ returns
     true
   end
 
+  def validate_preferences
+    return true if !changes
+    return true if !changes['preferences']
+    return true if preferences.blank?
+    return true if !preferences[:notification_sound]
+    return true if !preferences[:notification_sound][:enabled]
+    if preferences[:notification_sound][:enabled] == 'true'
+      preferences[:notification_sound][:enabled] = true
+    elsif preferences[:notification_sound][:enabled] == 'false'
+      preferences[:notification_sound][:enabled] = false
+    end
+    class_name = preferences[:notification_sound][:enabled].class.to_s
+    raise Exceptions::UnprocessableEntity, "preferences.notification_sound.enabled need to be an boolean, but it was a #{class_name}" if class_name != 'TrueClass' && class_name != 'FalseClass'
+    true
+  end
+
 =begin
 
 checks if the current user is the last one with admin permissions.
diff --git a/db/migrate/20180223000001_cleanup_user_preferences_notification_sound.rb b/db/migrate/20180223000001_cleanup_user_preferences_notification_sound.rb
deleted file mode 100644
index b7b4b71a4..000000000
--- a/db/migrate/20180223000001_cleanup_user_preferences_notification_sound.rb
+++ /dev/null
@@ -1,36 +0,0 @@
-class CleanupUserPreferencesNotificationSound < ActiveRecord::Migration[5.1]
-  def up
-    User.with_permissions('ticket.agent').each do |user|
-      local_to_h!(user.preferences)
-      user.save!
-    end
-
-    User.with_permissions('ticket.agent').each do |user|
-      next if !user.preferences
-      next if !user.preferences[:notification_sound]
-      next if !user.preferences[:notification_sound][:enabled]
-      if user.preferences[:notification_sound][:enabled] == 'true'
-        user.preferences[:notification_sound][:enabled] = true
-        user.save!
-        next
-      end
-      next if user.preferences[:notification_sound][:enabled] != 'false'
-      user.preferences[:notification_sound][:enabled] = false
-      user.save!
-      next
-    end
-  end
-
-  def local_to_h!(value)
-    if value.class == ActionController::Parameters
-      value = value.permit!.to_h
-    end
-    if value.class == Hash || value.class == ActiveSupport::HashWithIndifferentAccess
-      value.each_key do |local_key|
-        value[local_key] = local_to_h!(value[local_key])
-      end
-    end
-    value
-  end
-
-end
diff --git a/db/migrate/20180410000001_cleanup_user_preferences_notification_sound2.rb b/db/migrate/20180410000001_cleanup_user_preferences_notification_sound2.rb
new file mode 100644
index 000000000..c1f3ff976
--- /dev/null
+++ b/db/migrate/20180410000001_cleanup_user_preferences_notification_sound2.rb
@@ -0,0 +1,57 @@
+class CleanupUserPreferencesNotificationSound2 < ActiveRecord::Migration[5.1]
+
+  def local_to_h!(value)
+    if value.class == ActionController::Parameters
+      value = value.permit!.to_h
+    end
+    if value.class == Hash || value.class == ActiveSupport::HashWithIndifferentAccess
+      value.each_key do |local_key|
+        value[local_key] = local_to_h!(value[local_key])
+      end
+    end
+    value
+  end
+
+  def local_clear_preferences(user)
+    return false if !user
+    return false if !user.preferences
+    return false if !user.preferences[:notification_sound]
+    return false if !user.preferences[:notification_sound][:enabled]
+    if user.preferences[:notification_sound][:enabled] == 'true'
+      user.preferences[:notification_sound][:enabled] = true
+      user.save!
+      return true
+    end
+    return false if user.preferences[:notification_sound][:enabled] != 'false'
+    user.preferences[:notification_sound][:enabled] = false
+    user.save!
+    true
+  end
+
+  def up
+    User.with_permissions('ticket.agent').each do |user|
+      local_to_h!(user.preferences)
+      user.save!
+    end
+
+    items = SearchIndexBackend.search('preferences.notification_sound.enabled:*', 3000, 'User') || []
+    items.each do |item|
+      next if !item[:id]
+      user = User.find_by(id: item[:id])
+      local_to_h!(user.preferences)
+      local_clear_preferences(user)
+    end
+
+    Organization.all.each do |organization|
+      organization.members.each do |user|
+        local_to_h!(user.preferences)
+        local_clear_preferences(user)
+      end
+    end
+
+    Delayed::Job.all.each do |job|
+      Delayed::Worker.new.run(job)
+    end
+  end
+
+end
diff --git a/test/unit/user_test.rb b/test/unit/user_test.rb
index 6f9299a18..5e9b9b383 100644
--- a/test/unit/user_test.rb
+++ b/test/unit/user_test.rb
@@ -1063,4 +1063,112 @@ class UserTest < ActiveSupport::TestCase
     assert_equal(1, User.group_access(group.id, 'full').count)
   end
 
+  test 'preferences[:notification_sound][:enabled] value check' do
+    roles  = Role.where(name: 'Agent')
+    agent1 = User.create!(
+      login: "agent-default-preferences-1#{name}@example.com",
+      firstname: 'vaild_agent_group_permission-1',
+      lastname: "Agent#{name}",
+      email: "agent-default-preferences-1#{name}@example.com",
+      password: 'agentpw',
+      active: true,
+      roles: roles,
+      preferences: {
+        notification_sound: {
+          enabled: true,
+        }
+      },
+      updated_by_id: 1,
+      created_by_id: 1,
+    )
+    assert_equal(true, agent1.preferences[:notification_sound][:enabled])
+
+    agent2 = User.create!(
+      login: "agent-default-preferences-2#{name}@example.com",
+      firstname: 'vaild_agent_group_permission-2',
+      lastname: "Agent#{name}",
+      email: "agent-default-preferences-2#{name}@example.com",
+      password: 'agentpw',
+      active: true,
+      roles: roles,
+      preferences: {
+        notification_sound: {
+          enabled: false,
+        }
+      },
+      updated_by_id: 1,
+      created_by_id: 1,
+    )
+    assert_equal(false, agent2.preferences[:notification_sound][:enabled])
+
+    agent3 = User.create!(
+      login: "agent-default-preferences-3#{name}@example.com",
+      firstname: 'vaild_agent_group_permission-3',
+      lastname: "Agent#{name}",
+      email: "agent-default-preferences-3#{name}@example.com",
+      password: 'agentpw',
+      active: true,
+      roles: roles,
+      preferences: {
+        notification_sound: {
+          enabled: true,
+        }
+      },
+      updated_by_id: 1,
+      created_by_id: 1,
+    )
+    assert_equal(true, agent3.preferences[:notification_sound][:enabled])
+    agent3.preferences[:notification_sound][:enabled] = 'false'
+    agent3.save!
+    agent3.reload
+    assert_equal(false, agent3.preferences[:notification_sound][:enabled])
+
+    agent4 = User.create!(
+      login: "agent-default-preferences-4#{name}@example.com",
+      firstname: 'vaild_agent_group_permission-4',
+      lastname: "Agent#{name}",
+      email: "agent-default-preferences-4#{name}@example.com",
+      password: 'agentpw',
+      active: true,
+      roles: roles,
+      preferences: {
+        notification_sound: {
+          enabled: false,
+        }
+      },
+      updated_by_id: 1,
+      created_by_id: 1,
+    )
+    assert_equal(false, agent4.preferences[:notification_sound][:enabled])
+    agent4.preferences[:notification_sound][:enabled] = 'true'
+    agent4.save!
+    agent4.reload
+    assert_equal(true, agent4.preferences[:notification_sound][:enabled])
+
+    agent4.preferences[:notification_sound][:enabled] = 'invalid'
+    assert_raises(Exceptions::UnprocessableEntity) do
+      agent4.save!
+    end
+
+    assert_raises(Exceptions::UnprocessableEntity) do
+      User.create!(
+        login: "agent-default-preferences-5#{name}@example.com",
+        firstname: 'vaild_agent_group_permission-5',
+        lastname: "Agent#{name}",
+        email: "agent-default-preferences-5#{name}@example.com",
+        password: 'agentpw',
+        active: true,
+        roles: roles,
+        preferences: {
+          notification_sound: {
+            enabled: 'invalid string',
+          }
+        },
+        updated_by_id: 1,
+        created_by_id: 1,
+      )
+    end
+
+  end
+
 end